Anisotropic magnetic properties of the KMo4O6

NASA Astrophysics Data System (ADS)

Andrade, M.; Maffei, M. L.; Dos Santos, C. A. M.; Ferreira, B.; Sartori, A. F.

2012-02-01

Electrical resistivity measurements in the tetragonal KMo4O6 single crystals show a metal-insulator transition (MIT) near 100K. Magnetization measurements as a function of temperature show no evidence of magnetic ordering at this MIT [1]. Single crystals of KMo4O6 were obtained by electrolysis of a melt with a molar ratio of K2MoO4:MoO3 = 6:1. The process were carried out at 930 C with a current of 20-25mA for 52h in argon atmosphere. After that, electrodes were removed from the melt alloying the crystals to cool down to room temperature rapidly. Scanning Electron Microscopy (SEM) showed that the black single crystals were grown on the platinum cathode. Typical dimensions of the single crystals are 1x0.2x0.2mm^3. X-ray diffractometry confirmed that the single crystals have KMo4O6 tetragonal crystalline structure with space group P4. Magnetization measurements were performed parallel and perpendicular to the c-axis from 2 to 300K. The results show anisotropic behavior between both directions. Furthermore, the temperature independence of the magnetization at high temperature and the upturn at low temperature are observed in agreement with previous results [1]. MxH curves measured at several temperatures show nonlinear behavior and a small magnetic ordering. The magnetic ordering seems to be related to the MIT near 100K. This material is based upon support by FAPESP (2009/14524-6 and 2009/54001-6) and CNPq/NSF (490182/2009-7). M. Andrade is CAPES fellow and C.A.M. dos Santos is CNPq fellow. [4pt] [1] K. V. Ramanujachary et al., J. Sol. State Chem.102 (1993) 69.

Carbon-Free CoO Mesoporous Nanowire Array Cathode for High-Performance Aprotic Li-O2 Batteries.

PubMed

Wu, Baoshan; Zhang, Hongzhang; Zhou, Wei; Wang, Meiri; Li, Xianfeng; Zhang, Huamin

2015-10-21

Although various kinds of catalysts have been developed for aprotic Li-O2 battery application, the carbon-based cathodes are still vulnerable to attacks from the discharge intermediates or products, as well as the accompanying electrolyte decomposition. To ameliorate this problem, the free-standing and carbon-free CoO nanowire array cathode was purposely designed for Li-O2 batteries. The single CoO nanowire formed as a special mesoporous structure, owing even comparable specific surface area and pore volume to the typical Super-P carbon particles. In addition to the highly selective oxygen reduction/evolution reactions catalytic activity of CoO cathodes, both excellent discharge specific capacity and cycling efficiency of Li-O2 batteries were obtained, with 4888 mAh gCoO(-1) and 50 cycles during 500 h period. Owing to the synergistic effect between elaborate porous structure and selective intermediate absorption on CoO crystal, a unique bimodal growth phenomenon of discharge products was occasionally observed, which further offers a novel mechanism to control the formation/decomposition morphology of discharge products in nanoscale. This research work is believed to shed light on the future development of high-performance aprotic Li-O2 batteries.

Single Crystal Diamond Needle as Point Electron Source.

PubMed

Kleshch, Victor I; Purcell, Stephen T; Obraztsov, Alexander N

2016-10-12

Diamond has been considered to be one of the most attractive materials for cold-cathode applications during past two decades. However, its real application is hampered by the necessity to provide appropriate amount and transport of electrons to emitter surface which is usually achieved by using nanometer size or highly defective crystallites having much lower physical characteristics than the ideal diamond. Here, for the first time the use of single crystal diamond emitter with high aspect ratio as a point electron source is reported. Single crystal diamond needles were obtained by selective oxidation of polycrystalline diamond films produced by plasma enhanced chemical vapor deposition. Field emission currents and total electron energy distributions were measured for individual diamond needles as functions of extraction voltage and temperature. The needles demonstrate current saturation phenomenon and sensitivity of emission to temperature. The analysis of the voltage drops measured via electron energy analyzer shows that the conduction is provided by the surface of the diamond needles and is governed by Poole-Frenkel transport mechanism with characteristic trap energy of 0.2-0.3 eV. The temperature-sensitive FE characteristics of the diamond needles are of great interest for production of the point electron beam sources and sensors for vacuum electronics.

Single Crystal Diamond Needle as Point Electron Source

NASA Astrophysics Data System (ADS)

Kleshch, Victor I.; Purcell, Stephen T.; Obraztsov, Alexander N.

2016-10-01

Diamond has been considered to be one of the most attractive materials for cold-cathode applications during past two decades. However, its real application is hampered by the necessity to provide appropriate amount and transport of electrons to emitter surface which is usually achieved by using nanometer size or highly defective crystallites having much lower physical characteristics than the ideal diamond. Here, for the first time the use of single crystal diamond emitter with high aspect ratio as a point electron source is reported. Single crystal diamond needles were obtained by selective oxidation of polycrystalline diamond films produced by plasma enhanced chemical vapor deposition. Field emission currents and total electron energy distributions were measured for individual diamond needles as functions of extraction voltage and temperature. The needles demonstrate current saturation phenomenon and sensitivity of emission to temperature. The analysis of the voltage drops measured via electron energy analyzer shows that the conduction is provided by the surface of the diamond needles and is governed by Poole-Frenkel transport mechanism with characteristic trap energy of 0.2-0.3 eV. The temperature-sensitive FE characteristics of the diamond needles are of great interest for production of the point electron beam sources and sensors for vacuum electronics.

The High Performance of Crystal Water Containing Manganese Birnessite Cathodes for Magnesium Batteries.

PubMed

Nam, Kwan Woo; Kim, Sangryun; Lee, Soyeon; Salama, Michael; Shterenberg, Ivgeni; Gofer, Yossi; Kim, Joo-Seong; Yang, Eunjeong; Park, Chan Sun; Kim, Ju-Sik; Lee, Seok-Soo; Chang, Won-Seok; Doo, Seok-Gwang; Jo, Yong Nam; Jung, Yousung; Aurbach, Doron; Choi, Jang Wook

2015-06-10

Rechargeable magnesium batteries have lately received great attention for large-scale energy storage systems due to their high volumetric capacities, low materials cost, and safe characteristic. However, the bivalency of Mg(2+) ions has made it challenging to find cathode materials operating at high voltages with decent (de)intercalation kinetics. In an effort to overcome this challenge, we adopt an unconventional approach of engaging crystal water in the layered structure of Birnessite MnO2 because the crystal water can effectively screen electrostatic interactions between Mg(2+) ions and the host anions. The crucial role of the crystal water was revealed by directly visualizing its presence and dynamic rearrangement using scanning transmission electron microscopy (STEM). Moreover, the importance of lowering desolvation energy penalty at the cathode-electrolyte interface was elucidated by working with water containing nonaqueous electrolytes. In aqueous electrolytes, the decreased interfacial energy penalty by hydration of Mg(2+) allows Birnessite MnO2 to achieve a large reversible capacity (231.1 mAh g(-1)) at high operating voltage (2.8 V vs Mg/Mg(2+)) with excellent cycle life (62.5% retention after 10000 cycles), unveiling the importance of effective charge shielding in the host and facile Mg(2+) ions transfer through the cathode's interface.

Electrochemically assisted localized etching of ZnO single crystals in water using a catalytically active Pt-coated atomic force microscopy probe

NASA Astrophysics Data System (ADS)

Shibata, Takayuki; Yamamoto, Kota; Sasano, Junji; Nagai, Moeto

2017-09-01

This paper presents a nanofabrication technique based on the electrochemically assisted chemical dissolution of zinc oxide (ZnO) single crystals in water at room temperature using a catalytically active Pt-coated atomic force microscopy (AFM) probe. Fabricated grooves featured depths and widths of several tens and several hundreds of nanometers, respectively. The material removal rate of ZnO was dramatically improved by controlling the formation of hydrogen ions (H+) on the surface of the catalytic Pt-coated probe via oxidation of H2O molecules; this reaction can be enhanced by applying a cathodic potential to an additional Pt-wire working electrode in a three-electrode configuration. Consequently, ZnO can be dissolved chemically in water as a soluble Zn2+ species via a reaction with H+ species present in high concentrations in the immediate vicinity of the AFM tip apex.

Barium Transport Process in Impregnated Dispenser Cathodes.

DTIC Science & Technology

1982-01-25

experiments were carried out on pure tungsten. The tung- sten was either in the form of thin foils (6 mm on a side) or single crystal disks (6 mm in...temperature reveal the presence of car- bon, silicon , calcium, and nitrogen impurities, with only trace amounts (ɚ%) of calcium and nitrogen. Carbon is not...expected to be present at diffusion temperatures but forms as an overlayer only upon cooling [6]. We hope to re- duce silicon impurity levels by use of

Composition and Elution Behavior of Various Elements from Printed Circuit Boards, Cathode-ray Tube Glass, and Liquid-crystal Displays in Waste Consumer Electronics.

PubMed

Inaba, Kazuho; Murata, Tomoyoshi; Yamamura, Shigeki; Nagano, Masaaki; Iwasaki, Kazuhiro; Nakajima, Daisuke; Takigami, Hidetaka

2018-01-01

The contents and elution behavior of metals in consumer electronics parts were determined so as to understand their maximum environmental risk. Elements contained most in printed-circuit boards were Cu, Si, Br, Ca, Al, Sn, Pb, Sb, Ba, Fe, Ni, Ti, and Zn; in cathode-ray tube glass were Si, Pb, Ba, Sr, Zn, Zr, Ca, and Sb; in arsenic contained liquid-crystal displays were Si, Ca, Sr, Ba, As, and Fe; and in antimony contained liquid-crystal displays were Si, Ba, Ca, Sb, Sr, Fe, and Sn. The elements eluted most from printed-circuit boards were Zn, Pb, and Cu; from cathode-ray tube glass were Pb, Zn, B, Ba, and Si; and from liquid-crystal displays were B and Si, and the toxic As and Sb. The amount eluted was greatest at acidic pH. It was revealed that officially recommended 6-h-shaking with a pure water test was insufficient to understand the real environmental risk of waste electronics.

Synthesis, Characterization and Performance of Cathodes for Lithium Ion Batteries

NASA Astrophysics Data System (ADS)

Zhu, Jianxin

Lithium ion batteries provide a high energy density, higher voltage as well as a long shelf life compared to traditionally used lead acid, NiMH and NiCd batteries. Thus, they are a very promising energy storage system for our daily life. As one of the most important components in a battery, cathode materials have been investigated intensively in recent years as they play a key role in determining the cell voltage and discharge capacity in a battery. Both layered Li(Ni1/3Co1/3Mn1/3)O 2 (NCM) and olivine-structured LiFePO4 (LFP) materials are promising cathode candidates. However, these cathodes also have some disadvantages that have hindered further commercialization. The main issue with NCM is its rapid performance decay upon cycling. In addition, LFP is hindered by a low rate capacity and low lithium ion diffusivity. We studied the crystal growth behavior and performance of both Li(Ni 1/3Co1/3Mn1/3)O2 and LiFePO4 cathodes in order to develop synthesis-structure-function relationships. Three different crystal growth behaviors were observed for the NCM annealing process: surface, volume and grain boundary diffusion. Further exploration of the mechanism of NCM performance decay revealed that microstructural changes were related to the strain accommodation ability in this system and that nanostructured materials were more stable during cycling. In the LFP synthesis, we observed both oriented attachment (OA) and Ostwald ripening (OR) during growth in a triethylene-glycol system. Both polycrystalline and single crystalline particles evolved as a function of a time-dependent pH change. Thus, the lithium ion diffusion rate of LiFePO4 was improved by tailoring the morphology and size though our modification of the precursor environment, revealing that polycrystalline LFP displayed better performance than single crystalline particles. Finally, the electronic conductivity of LiFePO4 was successfully increased via a polymer solution coating method. By producing more uniform, thin and coherent coatings on LiFePO4 particles, we were able to produce batteries with significantly less carbon (i.e., 0.41 wt.%) while has comparable performance (discharge capacity of 80mAh/g at 2C) compared to traditionally synthesized carbon-coated LiFePO4 with higher carbon loadings (ca. 2.64 wt.%). This will enable us to produce batteries with higher active material loading and therefore, significantly larger energy densities.

Single Crystal Diamond Needle as Point Electron Source

PubMed Central

Kleshch, Victor I.; Purcell, Stephen T.; Obraztsov, Alexander N.

2016-01-01

Diamond has been considered to be one of the most attractive materials for cold-cathode applications during past two decades. However, its real application is hampered by the necessity to provide appropriate amount and transport of electrons to emitter surface which is usually achieved by using nanometer size or highly defective crystallites having much lower physical characteristics than the ideal diamond. Here, for the first time the use of single crystal diamond emitter with high aspect ratio as a point electron source is reported. Single crystal diamond needles were obtained by selective oxidation of polycrystalline diamond films produced by plasma enhanced chemical vapor deposition. Field emission currents and total electron energy distributions were measured for individual diamond needles as functions of extraction voltage and temperature. The needles demonstrate current saturation phenomenon and sensitivity of emission to temperature. The analysis of the voltage drops measured via electron energy analyzer shows that the conduction is provided by the surface of the diamond needles and is governed by Poole-Frenkel transport mechanism with characteristic trap energy of 0.2–0.3 eV. The temperature-sensitive FE characteristics of the diamond needles are of great interest for production of the point electron beam sources and sensors for vacuum electronics. PMID:27731379

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

Bolotnikov, A. E., E-mail: bolotnik@bnl.gov; Ackley, K.; Camarda, G. S.

We developed a robust and low-cost array of virtual Frisch-grid CdZnTe detectors coupled to a front-end readout application-specific integrated circuit (ASIC) for spectroscopy and imaging of gamma rays. The array operates as a self-reliant detector module. It is comprised of 36 close-packed 6 × 6 × 15 mm{sup 3} detectors grouped into 3 × 3 sub-arrays of 2 × 2 detectors with the common cathodes. The front-end analog ASIC accommodates up to 36 anode and 9 cathode inputs. Several detector modules can be integrated into a single- or multi-layer unit operating as a Compton or a coded-aperture camera. We presentmore » the results from testing two fully assembled modules and readout electronics. The further enhancement of the arrays’ performance and reduction of their cost are possible by using position-sensitive virtual Frisch-grid detectors, which allow for accurate corrections of the response of material non-uniformities caused by crystal defects.« less

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

Bolotnikov, A. E.; Ackley, K.; Camarda, G. S.

We developed a robust and low-cost array of virtual Frisch-grid CdZnTe (CZT) detectors coupled to a front-end readout ASIC for spectroscopy and imaging of gamma rays. The array operates as a self-reliant detector module. It is comprised of 36 close-packed 6x6x15 mm 3 detectors grouped into 3x3 sub-arrays of 2x2 detectors with the common cathodes. The front-end analog ASIC accommodates up to 36 anode and 9 cathode inputs. Several detector modules can be integrated into a single- or multi-layer unit operating as a Compton or a coded-aperture camera. We present the results from testing two fully assembled modules and readoutmore » electronics. The further enhancement of the arrays’ performance and reduction of their cost are made possible by using position-sensitive virtual Frisch-grid detectors, which allow for accurate corrections of the response of material non-uniformities caused by crystal defects.« less

High resolution x-ray absorption and emission spectroscopy of Li x CoO2 single crystals as a function delithiation

NASA Astrophysics Data System (ADS)

Simonelli, L.; Paris, E.; Iwai, C.; Miyoshi, K.; Takeuchi, J.; Mizokawa, T.; Saini, N. L.

2017-03-01

The effect of delithiation in Li x CoO2 is studied by high resolution Co K-edge x-ray absorption and x-ray emission spectroscopy. Polarization dependence of the x-ray absorption spectra on single crystal samples is exploited to reveal information on the anisotropic electronic structure. We find that the electronic structure of Li x CoO2 is significantly affected by delithiation in which the Co ions oxidation state tending to change from 3+  to 4+. The Co intersite (intrasite) 4p-3d hybridization suffers a decrease (increase) by delithiation. The unoccupied 3d t 2g orbitals with a 1g symmetry, containing substantial O 2p character, hybridize isotropically with Co 4p orbitals and likely to have itinerant character unlike anisotropically hybridized 3d e g orbitals. Such a peculiar electronic structure could have significant effect on the mobility of Li in Li x CoO2 cathode and hence the battery characteristics.

Nanomodulated electron beams via electron diffraction and emittance exchange for coherent x-ray generation

NASA Astrophysics Data System (ADS)

Nanni, E. A.; Graves, W. S.; Moncton, D. E.

2018-01-01

We present a new method for generation of relativistic electron beams with current modulation on the nanometer scale and below. The current modulation is produced by diffracting relativistic electrons in single crystal Si, accelerating the diffracted beam and imaging the crystal structure, then transferring the image into the temporal dimension via emittance exchange. The modulation period can be tuned by adjusting electron optics after diffraction. This tunable longitudinal modulation can have a period as short as a few angstroms, enabling production of coherent hard x-rays from a source based on inverse Compton scattering with total accelerator length of approximately ten meters. Electron beam simulations from cathode emission through diffraction, acceleration, and image formation with variable magnification are presented along with estimates of the coherent x-ray output properties.

Molten salt-directed synthesis method for LiMn2O4 nanorods as a cathode material for a lithium-ion battery with superior cyclability

NASA Astrophysics Data System (ADS)

Kebede, Mesfin A.; Ozoemena, Kenneth I.

2017-02-01

A molten salt synthesis technique has been used to prepare nanorods of Mn2O3 and single-crystal LiMn2O4 nanorods cathode material with superior capacity retention. The molten salt-directed synthesis involved the use of NaCl as the eutectic melt. The as-synthesized LiMn2O4 nanorods cathode material showed superior electrochemical performance compared to the LiMn2O4 sample obtained via the solid state method. The as-synthesized LiMn2O4 nanorods maintained more than 95% of the initial discharge capacity of 107 mA h g-1 over 100 cycles at a rate of 0.1 C, whereas the LiMn2O4 sample synthesized using the solid state reaction method maintained 88% of the initial discharge capacity of 98 mA h g-1 over 100 cycles at a rate of 0.1 C. Compared to the literature, the molten salt-directed method for the preparation of high-performance LiMn2O4 is simpler and less expensive, with greater potential for industrial scale-up.

In Situ Atomic-Scale Observation of Electrochemical Delithiation Induced Structure Evolution of LiCoO2 Cathode in a Working All-Solid-State Battery.

PubMed

Gong, Yue; Zhang, Jienan; Jiang, Liwei; Shi, Jin-An; Zhang, Qinghua; Yang, Zhenzhong; Zou, Dongli; Wang, Jiangyong; Yu, Xiqian; Xiao, Ruijuan; Hu, Yong-Sheng; Gu, Lin; Li, Hong; Chen, Liquan

2017-03-29

We report a method for in situ atomic-scale observation of electrochemical delithiation in a working all-solid-state battery using a state-of-the-art chip based in situ transmission electron microscopy (TEM) holder and focused ion beam milling to prepare an all-solid-state lithium-ion battery sample. A battery consisting of LiCoO 2 cathode, LLZO solid state electrolyte and gold anode was constructed, delithiated and observed in an aberration corrected scanning transmission electron microscope at atomic scale. We found that the pristine single crystal LiCoO 2 became nanosized polycrystal connected by coherent twin boundaries and antiphase domain boundaries after high voltage delithiation. This is different from liquid electrolyte batteries, where a series of phase transitions take place at LiCoO 2 cathode during delithiation. Both grain boundaries become more energy favorable along with extraction of lithium ions through theoretical calculation. We also proposed a lithium migration pathway before and after polycrystallization. This new methodology could stimulate atomic scale in situ scanning/TEM studies of battery materials and provide important mechanistic insight for designing better all-solid-state battery.

Increasing phosphorus recovery from dewatering centrate in microbial electrolysis cells.

PubMed

Yuan, Pengyi; Kim, Younggy

2017-01-01

Microbial electrolysis cells (MECs) use bioelectrochemical reactions to remove organic contaminants at the bioanode and produce hydrogen gas at the cathode. High local pH conditions near the cathode can also be utilized to produce struvite from nutrient-rich wastewater. This beneficial aspect was investigated using lab-scale MECs fed with dewatering centrate collected at a local wastewater treatment plant. The main objective was to improve phosphorus recovery by examining various cathode configurations and electric current conditions. The stainless steel mesh (SSM) cathode was relatively inefficient to achieve complete phosphorus recovery because struvite crystals were smaller (a few to tens of micrometers) than the open space between mesh wires (80 µm). As a result, the use of multiple pieces of SSM also showed a limited improvement in the phosphorus recovery up to only 68% with 5 SSM pieces. Readily available organic substrates were not sufficient in the dewatering centrate, resulting in relatively low electric current density (mostly below 0.2 A/m 2 ). The slow electrode reaction did not provide sufficiently high pH conditions near the cathode for complete recovery of phosphorus as struvite. Based on these findings, additional experiments were conducted using stainless steel foil (SSF) as the cathode and acetate (12 mM) as an additional organic substrate for exoelectrogens at the bioanode. With the high electric current (>2 A/m 2 ), a thick layer of struvite crystals was formed on the SSF cathode. The phosphorus recovery increased to 96% with the increasing MEC operation time from 1 to 7 days. With the high phosphorus recovery, estimated energy requirement was relatively low at 13.8 kWh (with acetate) and 0.30 kWh (without acetate) to produce 1 kg struvite from dewatering centrate. For efficient phosphorus recovery from real wastewater, a foil-type cathode is recommended to avoid potential losses of small struvite crystals. Also, presence of readily available organic substrates is important to maintain high electric current and establish high local pH conditions near the cathode. Struvite precipitation was relatively slow, requiring 7 days for nearly complete removal (92%) and recovery (96%). Future studies need to focus on shortening the time requirement.

Ultralong Lifespan and Ultrafast Li Storage: Single-Crystal LiFePO4 Nanomeshes.

PubMed

Zhang, Yan; Zhang, Hui Juan; Feng, Yang Yang; Fang, Ling; Wang, Yu

2016-01-27

A novel LiFePO4 material, in the shape of a nanomesh, has been rationally designed and synthesized based on the low crystal-mismatch strategy. The LiFePO4 nanomesh possesses several advantages in morphology and crystal structure, including a mesoporous structure, its crystal orientation that is along the [010] direction, and a shortened Li-ion diffusion path. These properties are favorable for their application as cathode in Li-ion batteries, as these will accelerate the Li-ion diffusion rate, improve the Li-ion exchange between the LiFePO4 nanomesh and the electrolyte, and reduce the Li-ion capacitive behavior during Li intercalation. So the LiFePO4 nanomesh exhibits a high specific capacity, enhanced rate capability, and strengthened cyclability. The method developed here can also be extended to other similar systems, for instance, LiMnPO4 , LiCoPO4 , and LiNiPO4 , and may find more applications in the designed synthesis of functional materials. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Revealing Anisotropic Spinel Formation on Pristine Li- and Mn-Rich Layered Oxide Surface and Its Impact on Cathode Performance

DOE PAGES

Kuppan, Saravanan; Shukla, Alpesh Khushalchand; Membreno, Daniel; ...

2017-01-06

Surface properties of cathode particles play important roles in the transport of ions and electrons and they may ultimately dominate cathode's performance and stability in lithium-ion batteries. Through the use of carefully prepared Li 1.2Ni 0.13Mn 0.54Co 0.13O 2 crystal samples with six distinct morphologies, surface transition-metal redox activities and crystal structural transformation are investigated as a function of surface area and surface crystalline orientation. Complementary depth-profiled core-level spectroscopy, namely, X-ray absorption spectroscopy, electron energy loss spectroscopy, and atomic-resolution scanning transmission electron microscopy, are applied in the study, presenting a fine example of combining advanced diagnostic techniques with a well-definedmore » model system of battery materials. Here, we report the following findings: (1) a thin layer of defective spinel with reduced transition metals, similar to what is reported on cycled conventional secondary particles in the literature, is found on pristine oxide surface even before cycling, and (2) surface crystal structure and chemical composition of both pristine and cycled particles are facet dependent. Oxide structural and cycling stabilities improve with maximum expression of surface facets stable against transition-metal reduction. Finally, the intricate relationships among morphology, surface reactivity and structural transformation, electrochemical performance, and stability of the cathode materials are revealed.« less

Nanomodulated electron beams via electron diffraction and emittance exchange for coherent x-ray generation

DOE PAGES

Nanni, E. A.; Graves, W. S.; Moncton, D. E.

2018-01-19

We present a new method for generation of relativistic electron beams with current modulation on the nanometer scale and below. The current modulation is produced by diffracting relativistic electrons in single crystal Si, accelerating the diffracted beam and imaging the crystal structure, then transferring the image into the temporal dimension via emittance exchange. The modulation period can be tuned by adjusting electron optics after diffraction. This tunable longitudinal modulation can have a period as short as a few angstroms, enabling production of coherent hard x-rays from a source based on inverse Compton scattering with total accelerator length of approximately tenmore » meters. Electron beam simulations from cathode emission through diffraction, acceleration, and image formation with variable magnification are presented along with estimates of the coherent x-ray output properties.« less

Nanomodulated electron beams via electron diffraction and emittance exchange for coherent x-ray generation

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

Nanni, E. A.; Graves, W. S.; Moncton, D. E.

We present a new method for generation of relativistic electron beams with current modulation on the nanometer scale and below. The current modulation is produced by diffracting relativistic electrons in single crystal Si, accelerating the diffracted beam and imaging the crystal structure, then transferring the image into the temporal dimension via emittance exchange. The modulation period can be tuned by adjusting electron optics after diffraction. This tunable longitudinal modulation can have a period as short as a few angstroms, enabling production of coherent hard x-rays from a source based on inverse Compton scattering with total accelerator length of approximately tenmore » meters. Electron beam simulations from cathode emission through diffraction, acceleration, and image formation with variable magnification are presented along with estimates of the coherent x-ray output properties.« less

Surface-plasmon enhanced photoemission of a silver nano-patterned photocathode

NASA Astrophysics Data System (ADS)

Zhang, Z.; Li, R.; To, H.; Andonian, G.; Pirez, E.; Meade, D.; Maxson, J.; Musumeci, P.

2017-09-01

Nano-patterned photocathodes (NPC) take advantage of plasmonic effects to resonantly increase absorption of light and localize electromagnetic field intensity on metal surfaces leading to surface-plasmon enhanced photoemission. In this paper, we report the status of NPC research at UCLA including in particular the optimization of the dimensions of a nanohole array on a silver wafer to enhance plasmonic response at 800 nm light, the development of a spectrally-resolved reflectivity measurement setup for quick nanopattern validation, and of a novel cathode plug to enable high power tests of NPCs on single crystal substrates in a high gradient radiofrequency gun.

N-type Cu2O doped activated carbon as catalyst for improving power generation of air cathode microbial fuel cells.

PubMed

Zhang, Xi; Li, Kexun; Yan, Pengyu; Liu, Ziqi; Pu, Liangtao

2015-01-01

A novel n-type Cu2O doped activated carbon (AC) air cathode (Cu/AC) was developed as an alternative to Pt electrode for oxygen reduction in microbial fuel cells (MFCs). The maximum power density of MFCs using this novel air cathode was as high as 1390±76mWm(-2), almost 59% higher than the bare AC air cathode. Specifically, the resistance including total resistance and charge transfer resistance significantly decreased comparing to the control. Tafel curve also showed the faster electro-transfer kinetics of Cu/AC with exchange current density of 1.03×10(-3)Acm(-2), which was 69% higher than the control. Ribbon-like Cu2O was deposited on the surface of AC with the mesopore surface area increasing. Cubic Cu2O crystals exclusively expose (111) planes with the interplanar crystal spacing of 2.48Å, which was the dominate active sites for oxygen reduction reaction (ORR). N-type Cu2O with oxygen vacancies played crucial roles in electrochemical catalytic activity. Copyright © 2015 Elsevier Ltd. All rights reserved.

Conducting glasses recovered from thin film transistor liquid crystal display wastes for dye-sensitized solar cell cathodes.

PubMed

Chen, C-C; Chang, F-C; Peng, C Y; Wang, H Paul

2015-01-01

Transparent conductive glasses such as thin film transistor (TFT) array and colour filter glasses were recovered from the TFT-liquid crystal display panel wastes by dismantling and sonic cleaning. Noble metals (i.e. platinum (Pt)) and indium tin oxide (ITO) are generally used in the cathode of a dye-sensitized solar cell (DSSC). To reduce the DSSC cost, Pt was replaced with nano nickel-encapsulated carbon-shell (Ni@C) nanoparticles, which were prepared by carbonization of Ni²⁺-β-cyclodextrin at 673 K for 2 h. The recovered conductive glasses were used in the DSSC electrodes in the substitution of relatively expensive ITO. Interestingly, the efficiency of the DSSC having the Ni@C-coated cathode is as high as 2.54%. Moreover, the cost of the DSSC using the recovered materials can be reduced by at least 24%.

An electrochemical cell with sapphire windows for operando synchrotron X-ray powder diffraction and spectroscopy studies of high-power and high-voltage electrodes for metal-ion batteries.

PubMed

Drozhzhin, Oleg A; Tereshchenko, Ivan V; Emerich, Hermann; Antipov, Evgeny V; Abakumov, Artem M; Chernyshov, Dmitry

2018-03-01

A new multi-purpose operando electrochemical cell was designed, constructed and tested on the Swiss-Norwegian Beamlines BM01 and BM31 at the European Synchrotron Radiation Facility. Single-crystal sapphire X-ray windows provide a good signal-to-noise ratio, excellent electrochemical contact because of the constant pressure between the electrodes, and perfect electrochemical stability at high potentials due to the inert and non-conductive nature of sapphire. Examination of the phase transformations in the Li 1-x Fe 0.5 Mn 0.5 PO 4 positive electrode (cathode) material at C/2 and 10C charge and discharge rates, and a study of the valence state of the Ni cations in the Li 1-x Ni 0.5 Mn 1.5 O 4 cathode material for Li-ion batteries, revealed the applicability of this novel cell design to diffraction and spectroscopic investigations of high-power/high-voltage electrodes for metal-ion batteries.

Unraveling the Role of Transport, Electrocatalysis, and Surface Science in the Solid Oxide Fuel Cell Cathode Oxygen Reduction Reaction

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

Gopalan, Srikanth

2017-04-06

This final report for project FE0009656 covers the period from 10/01/2012 to 09/30/2015 and covers research accomplishments on the effects of carbon dioxide on the surface composition and structure of cathode materials for solid oxide fuel cells (SOFCs), specifically La1-xSrxFeyCo1- yO3-δ (LSCF). Epitaxially deposited thin films of LSCF on various single-crystal substrates have revealed the selective segregation of strontium to the surface thereby resulting in a surface enrichment of strontium. The near surface compositional profile in the films have been measured using total x-ray fluorescence (TXRF), and show that the kinetics of strontium segregation are higher at higher partial pressuresmore » of carbon dioxide. Once the strontium segregates to the surface, it leads to the formation of precipitates of SrO which convert to SrCO3 in the presence of even modest concentrations of carbon dioxide in the atmosphere. This has important implications for the performance of SOFCs which is discussed in this report. These experimental observations have also been verified by Density Functional Theory calculations (DFT) which predict the conditions under which SrO and SrCO3 can occur in LSCF. Furthermore, a few cathode compositions which have received attention in the literature as alternatives to LSCF cathodes have been studied in this work and shown to be thermodynamically unstable under the operating conditions of the SOFCs.« less

Evaluation of niobium as candidate electrode material for DC high voltage photoelectron guns

DOE PAGES

BastaniNejad, M.; Mohamed, Md. Abdullah; Elmustafa, A. A.; ...

2012-08-17

In this study, the field emission characteristics of niobium electrodes were compared to those of stainless steel electrodes using a DC high voltage field emission test apparatus. A total of eight electrodes were evaluated: two 304 stainless steel electrodes polished to mirror-like finish with diamond grit and six niobium electrodes (two single-crystal, two large-grain and two fine-grain) that were chemically polished using a buffered-chemical acid solution. Upon the first application of high voltage, the best large-grain and single-crystal niobium electrodes performed better than the best stainless steel electrodes, exhibiting less field emission at comparable voltage and gradient. In all cases,more » field emission from electrodes (stainless steel and/or niobium) could be significantly reduced and sometimes completely eliminated, by introducing krypton gas into the vacuum chamber while the electrode was biased at high voltage. Of all the electrodes tested, a large-grain niobium electrode performed the best, exhibiting no measurable field emission (< 10 pA) at 225 kV with 20 mm cathode/anode gap, corresponding to a gradient of 18.7 MV/m.« less

Evaluation of Niobium as Candidate Electrode Material for DC High Voltage Photoelectron Guns

NASA Technical Reports Server (NTRS)

BastaniNejad, M.; Mohamed, Abdullah; Elmustafa, A. A.; Adderley, P.; Clark, J.; Covert, S.; Hansknecht, J.; Hernandez-Garcia, C.; Poelker, M.; Mammei, R.;

Determination of electrical properties of degraded mixed ionic conductors: Impedance studies with applied dc voltage

NASA Astrophysics Data System (ADS)

Bayer, T. J. M.; Carter, J. J.; Wang, Jian-Jun; Klein, Andreas; Chen, Long-Qing; Randall, C. A.

2017-12-01

Under electrical bias, mixed ionic conductors such as SrTiO3 are characterized by oxygen vacancy migration which leads to resistance degradation. The defect chemistry to describe the relationship between conductivity and oxygen vacancies is usually obtained by high temperature conductivity data or quenching experiments. These techniques can investigate the equilibrated state only. Here, we introduce a new approach using in-situ impedance studies with applied dc voltage to analyze the temperature dependent electrical properties of degraded SrTiO3 single crystals. This procedure is most beneficial since it includes electric field driven effects. The benefits of the approach are highlighted by comparing acceptor doped and undoped SrTiO3. This approach allows the determination of the temperature activation of both anodic and cathodic conductivity of Fe-doped SrTiO3 in the degraded state. The anodic activation energy matches well with the published results, while the activation energy of the degraded cathode region reported here is not in agreement with earlier assumptions. The specific discrepancies of the experimental data and the published defect chemistry are discussed, and a defect chemistry model that includes the strong temperature dependence of the electron conductivity in the cathode region is proposed.

Positioning true coincidences that undergo inter-and intra-crystal scatter for a sub-mm resolution cadmium zinc telluride-based PET system

NASA Astrophysics Data System (ADS)

Abbaszadeh, Shiva; Chinn, Garry; Levin, Craig S.

2018-01-01

The kinematics of Compton scatter can be used to estimate the interaction sequence of inter-crystal scatter interactions in 3D position-sensitive cadmium zinc telluride (CZT) detectors. However, in the case of intra-crystal scatter in a ‘cross-strip’ CZT detector slab, multiple anode and cathode strips may be triggered, creating position ambiguity due to uncertainty in possible combinations of anode-cathode pairings. As a consequence, methods such as energy-weighted centroid are not applicable to position the interactions. In practice, since the event position is uncertain, these intra-crystal scatters events are discarded. In this work, we studied using Compton kinematics and a ‘direction difference angle’ to provide a method to correctly identify the anode-cathode pair corresponding to the first interaction position in an intra-crystal scatter event. GATE simulation studies of a NEMA NU4 image quality phantom in a small animal positron emission tomography under development composed of 192, 40~mm×40~mm×5 mm CZT crystals shows that 47% of total numbers of multiple-interaction photon events (MIPEs) are intra-crystal scatter with a 100 keV lower energy threshold per interaction. The sensitivity of the system increases from 0.6 to 4.10 (using 10 keV as system lower energy threshold) by including rather than discarding inter- and intra-crystal scatter. The contrast-to-noise ratio (CNR) also increases from 5.81+/-0.3 to 12.53+/-0.37 . It was shown that a higher energy threshold limits the capability of the system to detect MIPEs and reduces CNR. Results indicate a sensitivity increase (4.1 to 5.88) when raising the lower energy threshold (10 keV to 100 keV) for the case of only two-interaction events. In order to detect MIPEs accurately, a low noise system capable of a low energy threshold (10 keV) per interaction is desired.

Optical profiles of cathode ray tube and liquid crystal display monitors: implication in cutaneous phototoxicity in photodynamic therapy

PubMed Central

Lei, Tim C.; Pendyala, Srinivas; Scherrer, Larry; Li, Buhong; Glazner, Gregory F.; Huang, Zheng

2016-01-01

Recent clinical reports suggest that overexposure to light emissions generated from cathode ray tube (CRT) and liquid crystal display (LCD) color monitors after topical or systemic administration of a photosensitizer could cause noticeable skin phototoxicity. In this study, we examined the light emission profiles (optical irradiance, spectral irradiance) of CRT and LCD monitors under simulated movie and video game modes. Results suggest that peak emissions and integrated fluence generated from monitors are clinically relevant and therefore prolonged exposure to these light sources at a close distance should be avoided after the administration of a photosensitizer or phototoxic drug. PMID:23669681

Electrode Modification and Optimization in Air-Cathode Single-Chamber Microbial Fuel Cells.

PubMed

Wang, Yanhua; Wu, Jiayan; Yang, Shengke; Li, Huihui; Li, Xiaoping

2018-06-27

Due to the known problems of microbial fuel cells (MFCs), such as low electricity generation performance and high cost of operation, we modified the electrode with graphene and polyaniline (PANI) is a single-chamber air-cathode MFC and then evaluated the effects of electrode modification on MFC electricity generation performance. Carbon cloth electrodes (unmodified, CC; graphene-modified, G/CC; and polyaniline-graphene-modified, PANI-G/CC) were prepared using the impregnation method. Sulfonated cobalt phthalocyanine (CoPcS) was then introduced as a cathode catalyst. The Co-PANI-G/CC cathode showed higher catalytic activity toward oxygen reduction compared with other electrodes. The maximum power density of the MFC with Co-PANI-G/CC cathode was 32.2 mW/m², which was 1.8 and 6.1 times higher than the value obtained with Co-G/CC and Co/CC cathodes, respectively. This indicates a significant improvement in the electricity generation of single-chamber MFCs and provides a simple, effective cathode modification method. Furthermore, we constructed single-chamber MFCs using the modified anode and cathode and analyzed electricity generation and oxytetracycline (OTC) degradation with different concentrations of OTC as the fuel. With increasing added OTC concentration, the MFC performance in both electricity generation and OTC degradation gradually decreased. However, when less than 50 mg/L OTC was added, the 5-day degradation rate of OTC reached more than 90%. It is thus feasible to process OTC-containing wastewater and produce electricity using single-chamber MFCs, which provides a new concept for wastewater treatment.

Extended-testing of xenon ion thruster hollow cathodes

NASA Technical Reports Server (NTRS)

Sarver-Verhey, Timothy R.

1992-01-01

A hollow cathode wear-test of 508 hours was successfully completed at an emission current of 23.0 A and a xenon flow rate of 10 Pa-L/s. This test was the continuation of a hollow cathode contamination investigation. Discharge voltage was stable at 16.7 V. The cathode temperature averaged 1050 C with a 7 percent drop during the wear-test. Discharge ignition voltage was found to be approximately 20 V and was repeatable over four starts. Post-test analyses of the hollow cathode found a much improved internal cathode condition with respect to earlier wear-test cathodes. Negligible tungsten movement occurred and no formation of mono-barium tungsten was observed. These results correlated with an order-of-magnitude reduction in propellant feed-system leakage rate. Ba2CaWO6 and extensive calcium crystal formation occurred on the upstream end of the insert. Ba-Ca compound depositions were found on the Mo insert collar, on the Re electrical leads, and in the gap between the insert and cathode wall. This wear-test cathode was found to be in the best internal condition and had the most stable operating performance of any hollow cathode tested during this contamination investigation.

A new design of indirectly heated cathode based strip type electron gun.

PubMed

Maiti, Namita; Lijeesh, K; Barve, U D; Quadri, Nishad; Tembhare, G U; Mukherjee, S; Thakur, K B; Das, A K

2013-08-01

A new design of indirectly heated solid cathode based electron gun (200 kW, 45 kV, 270° bent strip type electron gun) has been presented. The design issue addressed is the uniformity of temperature on the solid cathode using (a) a multi-segmented filament with variable height as the primary heat source and (b) trapezoidal shaped single long filament as the primary heat source. The proposed design in this paper is based on computer simulation and validated by extensive experimentations. The design emphasis is on maintaining uniform temperature on the solid cathode. The designed multi-segment filament and the single long filament provide a temperature uniformity on the solid cathode of about 250 K and 110 K, respectively. The better temperature uniformity inspite of the thermal expansion, in case of a single long filament tightly clamped at two ends, has been possible due to shaping of the single filament with a number of constituent sections such that the thermal expansion of different sections forming the actual filament takes care of not only the mechanical stability but also does not affect the emitting surface of the filament. Experiments show that the modified design achieves a one to one correspondence of the solid cathode length and the electron beam length emitted from the solid cathode.

Modeling and validation of single-chamber microbial fuel cell cathode biofilm growth and response to oxidant gas composition

NASA Astrophysics Data System (ADS)

Ou, Shiqi; Zhao, Yi; Aaron, Douglas S.; Regan, John M.; Mench, Matthew M.

2016-10-01

This work describes experiments and computational simulations to analyze single-chamber, air-cathode microbial fuel cell (MFC) performance and cathodic limitations in terms of current generation, power output, mass transport, biomass competition, and biofilm growth. Steady-state and transient cathode models were developed and experimentally validated. Two cathode gas mixtures were used to explore oxygen transport in the cathode: the MFCs exposed to a helium-oxygen mixture (heliox) produced higher current and power output than the group of MFCs exposed to air or a nitrogen-oxygen mixture (nitrox), indicating a dependence on gas-phase transport in the cathode. Multi-substance transport, biological reactions, and electrochemical reactions in a multi-layer and multi-biomass cathode biofilm were also simulated in a transient model. The transient model described biofilm growth over 15 days while providing insight into mass transport and cathodic dissolved species concentration profiles during biofilm growth. Simulation results predict that the dissolved oxygen content and diffusion in the cathode are key parameters affecting the power output of the air-cathode MFC system, with greater oxygen content in the cathode resulting in increased power output and fully-matured biomass.

Modeling and validation of single-chamber microbial fuel cell cathode biofilm growth and response to oxidant gas composition

DOE PAGES

Ou, Shiqi; Zhao, Yi; Aaron, Douglas S.; ...

2016-08-15

This work describes experiments and computational simulations to analyze single-chamber, air-cathode microbial fuel cell (MFC) performance and cathodic limitations in terms of current generation, power output, mass transport, biomass competition, and biofilm growth. Steady-state and transient cathode models were developed and experimentally validated. Two cathode gas mixtures were used to explore oxygen transport in the cathode: the MFCs exposed to a helium-oxygen mixture (heliox) produced higher current and power output than the group of MFCs exposed to air or a nitrogen-oxygen mixture (nitrox), indicating a dependence on gas-phase transport in the cathode. Multi-substance transport, biological reactions, and electrochemical reactions inmore » a multi-layer and multi-biomass cathode biofilm were also simulated in a transient model. The transient model described biofilm growth over 15 days while providing insight into mass transport and cathodic dissolved species concentration profiles during biofilm growth. Lastly, simulation results predict that the dissolved oxygen content and diffusion in the cathode are key parameters affecting the power output of the air-cathode MFC system, with greater oxygen content in the cathode resulting in increased power output and fully-matured biomass.« less

On the tungsten single crystal coatings achieved by chemical vapor transportation deposition

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

Shi, J.Q.; Shen, Y.B.; Yao, S.Y.

2016-12-15

The tungsten single crystal has many excellent properties, namely a high melting point, high anti-creeping strength. Chemical vapor transportation deposition (CVTD) is a possible approach to achieve large-sized W single crystals for high-temperature application such as the cathode of a thermionic energy converter. In this work, CVTD W coatings were deposited on the monocrystalline molybdenum substrate (a tube with < 111 > axial crystalline orientation) using WCl{sub 6} as a transport medium. The microstructures of the coatings were investigated by a scanning electron microscope (SEM) and electron backscatter diffraction (EBSD). The as-deposited coatings are hexagonal prisms—rough surfaces perpendicular to with alternating hill-like bulges and pits at the side edges of the prisms, and flat surfaces perpendicular to < 112 > with arc-shaped terraces at the side faces. This can be explained by two-dimensional nucleation -mediated lateral growth model. Some parts of the coatings contain hillocks of an exotic morphology (noted as “abnormal growth”). The authors hypothesize that the abnormal growth is likely caused by the defects of the Mo substrate, which facilitate W nucleation sites, cause orientation difference, and may even form boundaries in the coatings. A dislocation density of 10{sup 6} to 10{sup 7} (counts/cm{sup 2}) was revealed by an etch-pit method and synchrotron X-ray diffraction. As the depositing temperature rises, the dislocation density decreases, and no sub-boundaries are found on samples deposited over 1300 °C, as a result of atom diffusion and dislocation climbing. - Highlights: •The varied growth rate causes the different morphologies of different planes. •The W coating is a single crystal when only single hillocks appear. •The (110) plane tends to have the lowest dislocation density. •The dislocation density tends to decrease as the temperature increases.« less

High rate, long cycle life battery electrode materials with an open framework structure

DOEpatents

Wessells, Colin; Huggins, Robert; Cui, Yi; Pasta, Mauro

2015-02-10

A battery includes a cathode, an anode, and an aqueous electrolyte disposed between the cathode and the anode and including a cation A. At least one of the cathode and the anode includes an electrode material having an open framework crystal structure into which the cation A is reversibly inserted during operation of the battery. The battery has a reference specific capacity when cycled at a reference rate, and at least 75% of the reference specific capacity is retained when the battery is cycled at 10 times the reference rate.

Effect of ‘A’-site non stoichiometry in strontium doped lanthanum ferrite based solid oxide fuel cell cathodes

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

Banerjee, Koyel; Mukhopadhyay, Jayanta, E-mail: jayanta_mu@cgcri.res.in; Barman, Madhurima

2015-12-15

Highlights: • La{sub 1−x}Sr{sub x}Co{sub y}Fe{sub 1−y}O{sub 3−δ}, x = 0.4; y = 0.2 system varying La-site (0.6–0.54) are studied. • Combustion synthesis technique is used to prepare the powder samples. • Highest electrical conductivity observed with largest A-site deficit composition. • Lowest cathode polarization is found with the same composition (0.02 Ω cm{sup 2}). • Composition with largest A-site deficiency exhibits best performance (2.84 A cm{sup −2}). - Abstract: Effect of A-site non-stoichiometry in strontium doped lanthanum cobalt ferrite (La{sub 1−x}Sr{sub x}Co{sub y}Fe{sub 1−y}O{sub 3−δ}, x = 0.4; y = 0.2) is studied in a systematic manner with variationmore » of ‘A’ site stoichiometry from 1 to 0.94. The perovskite based cathode compositions are synthesized by combustion synthesis. Powder characterizations reveal rhombohedral crystal structure with crystallite size ranging from 29 to 34 nm with minimum lattice spacing of 0.271 nm. Detailed sintering studies along with total DC electrical conductivities are evaluated in the bulk form with variation of sintering temperatures. The electrode polarizations are measured in the symmetric cell configuration by impedance spectroscopy which is found to be the lowest (0.02 Ω cm{sup 2} at 800 °C) for cathode having highest degree of ‘A’-site deficiency. The same cathode composition exhibits a current density of 2.84 A cm{sup −2} (at 0.7 V, 800 °C) in anode-supported single cell. An attempt has been made to correlate the trend of electrical behaviour with increasing ‘A’-site deficiency for such cathode compositions.« less

Molecular dynamics simulations of lithium silicate/vanadium pentoxide interfacial lithium ion diffusion in thin film lithium ion-conducting devices

NASA Astrophysics Data System (ADS)

Li, Weiqun

The lithium ion diffusion behavior and mechanism in the glassy electrolyte and the electrolyte/cathode interface during the initial stage of lithium ion diffusing from electrolyte into cathode were investigated using Molecular Dynamics simulation technique. Lithium aluminosilicate glass electrolytes with different R (ratio of the concentration of Al to Li) were simulated. The structural features of the simulated glasses are analyzed using Radial Distribution Function (RDF) and Pair Distribution Function (PDF). The diffusion coefficient and activation energy of lithium ion diffusion in simulated lithium aluminosilicate glasses were calculated and the values are consistent with those in experimental glasses. The behavior of lithium ion diffusion from the glassy electrolyte into a polycrystalline layered intercalation cathode has been studied. The solid electrolyte was a model lithium silicate glass while the cathode was a nanocrystalline vanadia with amorphous V2O5 intergranular films (IGF) between the V2O5 crystals. Two different orientations between the V2O5 crystal planes are presented for lithium ion intercalation via the amorphous vanadia IGF. A series of polycrystalline vanadia cathodes with 1.3, 1.9, 2.9 and 4.4 nm thickness IGFs were simulated to examine the effects of the IGF thickness on lithium ion transport in the polycrystalline vanadia cathodes. The simulated results showed that the lithium ions diffused from the glassy electrolyte into the IGF of the polycrystalline vanadia cathode and then part of those lithium ions diffused into the crystalline V2O5 from the IGF. The simulated results also showed an ordering of the vanadium ion structure in the IGF near the IGF/V2 O5 interface. The ordering structure still existed with glass former silica additive in IGF. Additionally, 2.9 run is suggested to be the optimal thickness of the IGF, which is neither too thick to decrease the capacity of the cathode nor too thin to impede the transport of lithium from glassy electrolyte into the cathode. Parallel molecular dynamic simulation technique was also used for a larger electrolyte/cathode interface system, which include more atoms and more complicated microstructures. Simulation results from larger electrolyte/cathode interface system prove that there is no size effect on simulation of smaller electrolyte/cathode interface system from statistical point of view.

Emission and evaporation properties of 75 at.% Re-25 at.% W mixed matrix impregnated cathode

NASA Astrophysics Data System (ADS)

Lai, Chen; Wang, Jinshu; Zhou, Fan; Liu, Wei; den Engelsen, Daniel; Miao, Naihua

2018-01-01

We present a comprehensive study on the phase, emission performance, surface composition, chemical states and evaporation properties of a 75 at.% Re-25 at.% W (75Re) mixed matrix impregnated cathode by several modern analyzers, including XRD, electron emission test device, in situ AES, XPS and Quartz Crystal Oscillation Instrument (QCOI). On the basis of experimental results, the adsorption energy and charge transfer of the Ba-O dipole adsorbed on cathode surface was investigated by the first-principles density functional theory calculations. The in situ AES analyses indicate that the atomic ratio of Ba:O of the active emission layer on the cathode surface converged to 3:2 for a conventional Ba-W cathode and to about 3:1 for the 75Re cathode. Due to the larger adsorption energy of Ba and Ba-O on 75Re cathode surface, the total evaporation rate of Ba and BaO in the 75Re cathode is much lower than that for the Ba-W cathode, which is agreed favorably with the experimental evaporation data. Our characterizations and calculations suggest that rhenium in the matrix of impregnated cathodes improves the stability of Ba-O dipole on the cathode surface and enhances the emission capability substantially.

Surface-plasmon enhanced photoemission of a silver nano-patterned photocathode

DOE PAGES

Zhang, Z.; Li, R.; To, H.; ...

2016-11-22

Here, nano-patterned photocathodes (NPC) take advantage of plasmonic effects to resonantly increase absorption of light and localize electromagnetic field intensity on metal surfaces leading to surface-plasmon enhanced photoemission. In this paper, we report the status of NPC research at UCLA including in particular the optimization of the dimensions of a nanohole array on a silver wafer to enhance plasmonic response at 800 nm light, the development of a spectrally-resolved reflectivity measurement setup for quick nanopattern validation, and of a novel cathode plug to enable high power tests of NPCs on single crystal substrates in a high gradient radiofrequency gun.

The aqueous electrochemistry of carbon-based surfaces-investigation by scanning tunneling microscopy

NASA Astrophysics Data System (ADS)

Mühl, T.; Myhra, S.

2007-04-01

Electro-oxidation of carbon-based materials will lead to conversion of the solid to CO2/CO at the anode, with H2 being produced at the cathode. Recent voltammetric investigations of carbon nano-tubes and single crystal graphite have shown that only edge sites and other defect sites are electrochemically active. Local oxidation of diamond-like carbon films (DLC) by an STM tip in moist air followed by imaging allows correlation of topographical change with electro-chemical conditions and surface reactivity. The results may have implications for lithographic processing of carbon surfaces, and may have relevance for electrochemical H2 production.

Surface-plasmon enhanced photoemission of a silver nano-patterned photocathode

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

Zhang, Z.; Li, R.; To, H.

Here, nano-patterned photocathodes (NPC) take advantage of plasmonic effects to resonantly increase absorption of light and localize electromagnetic field intensity on metal surfaces leading to surface-plasmon enhanced photoemission. In this paper, we report the status of NPC research at UCLA including in particular the optimization of the dimensions of a nanohole array on a silver wafer to enhance plasmonic response at 800 nm light, the development of a spectrally-resolved reflectivity measurement setup for quick nanopattern validation, and of a novel cathode plug to enable high power tests of NPCs on single crystal substrates in a high gradient radiofrequency gun.

Synthesis and bioelectrochemical behavior of aromatic amines.

PubMed

Shabbir, Muhammad; Akhter, Zareen; Ahmad, Iqbal; Ahmed, Safeer; Bolte, Michael; McKee, Vickie

2017-12-01

Four aromatic amines 1-amino-4-phenoxybenzene (A 1 ), 4-(4-aminophenyloxy) biphenyl (A 2 ), 1-(4-aminophenoxy) naphthalene (A 3 ) and 2-(4-aminophenoxy) naphthalene (A 4 ) were synthesized and characterized by elemental, spectroscopic (FTIR, NMR), mass spectrometric and single crystal X-ray diffraction methods. The compounds crystallized in monoclinic crystal system with space group P2 1 . Intermolecular hydrogen bonds were observed between the amine group and amine/ether acceptors of neighboring molecules. Electrochemical investigations were done using cyclic voltammetry (CV), square wave voltammetry (SWV) and differential pulse voltammetry (DPV). CV studies showed that oxidation of aromatic amines takes place at about 0.9 V (vs. Ag/AgCl) and the electron transfer (ET) process has irreversible nature. After first scan reactive intermediate were generated electrochemically and some other cathodic and anodic peaks also appeared in the succeeding scans. DPV study revealed that ET process is accompanied by one electron. DNA binding study of aromatic amines was performed by CV and UV-visible spectroscopy. These investigations revealed groove binding mode of interaction of aromatic amines with DNA. Copyright © 2017 Elsevier Inc. All rights reserved.

Unravelling structural ambiguities in lithium- and manganese-rich transition metal oxides

DOE PAGES

Shukla, Alpesh Khushalchand; Ramasse, Quentin M.; Ophus, Colin; ...

2015-10-29

Although Li- and Mn-rich transition metal oxides have been extensively studied as high-capacity cathode materials for Li-ion batteries, the crystal structure of these materials in their pristine state is not yet fully understood. Here we apply complementary electron microscopy and spectroscopy techniques at multi-length scale on well-formed Li1.2(Ni0.13Mn0.54Co0.13)O2 crystals with two different morphologies as well as two commercially available materials with similar compositions, and unambiguously describe the structural make-up of these samples. Systematically observing the entire primary particles along multiple zone axes reveals that they are consistently made up of a single phase, save for rare localized defects and amore » thin surface layer on certain crystallographic facets. Finally and more specifically, we show the bulk of the oxides can be described as an aperiodic crystal consisting of randomly stacked domains that correspond to three variants of monoclinic structure, while the surface is composed of a Co- and/or Ni-rich spinel with antisite defects.« less

Controlled crystallization and granulation of nano-scale β-Ni(OH) 2 cathode materials for high power Ni-MH batteries

NASA Astrophysics Data System (ADS)

He, Xiangming; Li, Jianjun; Cheng, Hongwei; Jiang, Changyin; Wan, Chunrong

A novel synthesis of controlled crystallization and granulation was attempted to prepare nano-scale β-Ni(OH) 2 cathode materials for high power Ni-MH batteries. Nano-scale β-Ni(OH) 2 and Co(OH) 2 with a diameter of 20 nm were prepared by controlled crystallization, mixed by ball milling, and granulated to form about 5 μm spherical grains by spray drying granulation. Both the addition of nano-scale Co(OH) 2 and granulation significantly enhanced electrochemical performance of nano-scale Ni(OH) 2. The XRD and TEM analysis shown that there were a large amount of defects among the crystal lattice of as-prepared nano-scale Ni(OH) 2, and the DTA-TG analysis shown that it had both lower decomposition temperature and higher decomposition reaction rate, indicating less thermal stability, as compared with conventional micro-scale Ni(OH) 2, and indicating that it had higher electrochemical performance. The granulated grains of nano-scale Ni(OH) 2 mixed with nano-scale Co(OH) 2 at Co/Ni = 1/20 presented the highest specific capacity reaching its theoretical value of 289 mAh g -1 at 1 C, and also exhibited much improved electrochemical performance at high discharge capacity rate up to 10 C. The granulated grains of nano-scale β-Ni(OH) 2 mixed with nano-scale Co(OH) 2 is a promising cathode active material for high power Ni-MH batteries.

Theoretical and experimental investigation into high current hollow cathode arc attachment

NASA Astrophysics Data System (ADS)

Downey, Ryan T.

This research addresses several concerns of the mechanisms controlling performance and lifetime of high-current single-channel-hollow-cathodes, the central electrode and primary life-limiting component in Magnetoplasmadynamic thrusters. Specifically covered are the trends, and the theorized governing mechanisms, seen in the discharge efficiency and power, the size of the plasma attachment to the cathode (the active zone), cathode exit plume plasma density and energy, along with plasma property distributions of the internal plasma column (the IPC) of a single-channel-hollow-cathode. Both experiment and computational modeling were employed in the analysis of the cathodes. Employing Tantalum and Tungsten cathodes (of 2, 6 and 10 mm inner diameter), experiments were conducted to measure the temperature profile of operating cathodes, the width of the active zone, the discharge voltage, power, plasma arc resistance and efficiency, with mass flow rates of 50 to 300 sccm of Argon, and discharge currents of 15 to 50 Amps. Langmuir probing was used to obtain measurements for the electron temperature, plasma density and plasma potential at the cathode exit plane (down stream tip). A computational model was developed to predict the distribution of plasma inside the cathode, based upon experimentally determined boundary conditions. It was determined that the peak cathode temperature is a function of both interior cathode density and discharge current, though the location of the peak temperature is controlled gas density but not discharge current. The active zone width was found to be an increasing function of the discharge current, but a decreasing function of the mass flow rate. The width of the active zone was found to not be controlled by the magnitude of the peak cathode wall temperature. The discharge power consumed per unit of mass throughput is seen as a decreasing function of the mass flow rate, showing the increasing efficiency of the cathode. Finally, this new understanding of the mechanisms of the plasma attachment phenomena of a single-channel-hollow-cathode were extrapolated to the multi-channel-hollow-cathode environment, to explain performance characteristics of these devices seen in previous research.

Site-specific transition metal occupation in multicomponent pyrophosphate for improved electrochemical and thermal properties in lithium battery cathodes: a combined experimental and theoretical study.

PubMed

Shakoor, Rana A; Kim, Heejin; Cho, Woosuk; Lim, Soo Yeon; Song, Hannah; Lee, Jung Woo; Kang, Jeung Ku; Kim, Yong-Tae; Jung, Yousung; Choi, Jang Wook

2012-07-18

As an attempt to develop lithium ion batteries with excellent performance, which is desirable for a variety of applications including mobile electronics, electrical vehicles, and utility grids, the battery community has continuously pursued cathode materials that function at higher potentials with efficient kinetics for lithium insertion and extraction. By employing both experimental and theoretical tools, herein we report multicomponent pyrophosphate (Li(2)MP(2)O(7), M = Fe(1/3)Mn(1/3)Co(1/3)) cathode materials with novel and advantageous properties as compared to the single-component analogues and other multicomponent polyanions. Li(2)Fe(1/3)Mn(1/3)Co(1/3)P(2)O(7) is formed on the basis of a solid solution among the three individual transition-metal-based pyrophosphates. The unique crystal structure of pyrophosphate and the first principles calculations show that different transition metals have a tendency to preferentially occupy either octahedral or pyramidal sites, and this site-specific transition metal occupation leads to significant improvements in various battery properties: a single-phase mode for Li insertion/extraction, improved cell potentials for Fe(2+)/Fe(3+) (raised by 0.18 eV) and Co(2+)/Co(3+) (lowered by 0.26 eV), and increased activity for Mn(2+)/Mn(3+) with significantly reduced overpotential. We reveal that the favorable energy of transition metal mixing and the sequential redox reaction for each TM element with a sufficient redox gap is the underlying physical reason for the preferential single-phase mode of Li intercalation/deintercalation reaction in pyrophosphate, a general concept that can be applied to other multicomponent systems. Furthermore, an extremely small volume change of ~0.7% between the fully charged and discharged states and the significantly enhanced thermal stability are observed for the present material, the effects unseen in previous multicomponent battery materials.

Spatiotemporal character of the Bobylev-Pikin flexoelectric instability in a twisted nematic bent-core liquid crystal exposed to very low frequency fields.

PubMed

Krishnamurthy, K S

2014-05-01

The Bobylev-Pikin striped-pattern state induced by a homogeneous electric field is a volume flexoelectric instability, originating in the midregion of a planarly aligned nematic liquid crystal layer. We find that the instability acquires a spatiotemporal character upon excitation by a low frequency (0.5 Hz) square wave field. This is demonstrated using a bent-core liquid crystal, initially in the 90°-twisted planar configuration. The flexoelectric modulation appears close to the cathode at each polarity reversal and, at low voltage amplitudes, decays completely as the field becomes steady. Correspondingly, at successive polarity changes, the stripe direction switches between the alignment directions at the two substrates. For large voltages, the stripes formed nearly along the alignment direction at the cathode gradually reorient toward the midplane director. These observations are generally attributed to inhomogeneous and time-dependent field conditions that come to exist after each polarity reversal. Polarity dependence of the instability is attributed to the formation of intrinsic double layers that bring about an asymmetry in surface fields. Momentary field elevation near the cathode following a voltage sign reversal and concomitant gradient flexoelectric polarization are considered the key factors in accounting for the surfacelike modulation observed at low voltages.

Single chamber microbial fuel cell with Ni-Co cathode

NASA Astrophysics Data System (ADS)

Włodarczyk, Barbara; Włodarczyk, Paweł P.; Kalinichenko, Antonina

2017-10-01

The possibility of wastewater treatment and the parallel energy production using the Ni-Co alloy as cathode catalyst for single chamber microbial fuel cells is presented in this research. The research included a preparation of catalyst and comparison of COD, NH4+ and NO3- reduction in the reactor without aeration, with aeration and with using a single chamber microbial fuel cell with Ni-Co cathode. The reduction time for COD with the use of microbial fuel cell with the Ni-Co catalyst is similar to the reduction time with aeration. The current density (2.4 A·m-2) and amount of energy (0.48 Wh) obtained in MFC is low, but the obtained amount of energy allows elimination of the energy needed for reactor aeration. It has been shown that the Ni-Co can be used as cathode catalyst in single chamber microbial fuel cells.

Solid oxide fuel cell with multi-unit construction and prismatic design

DOEpatents

McPheeters, Charles C.; Dees, Dennis W.; Myles, Kevin M.

1999-01-01

A single cell unit of a solid oxide fuel cell that is individually fabricated and sintered prior to being connected to adjacent cells to form a solid oxide fuel cell. The single cell unit is comprised of a shaped anode sheet positioned between a flat anode sheet and an anode-electrolyte-cathode (A/E/C) sheet, and a shaped cathode sheet positioned between the A/E/C sheet and a cathode-interconnect-anode (C/I/A) sheet. An alternate embodiment comprises a shaped cathode sheet positioned between an A/E/C sheet and a C/I/A sheet. The shaped sheets form channels for conducting reactant gases. Each single cell unit is individually sintered to form a finished sub-assembly. The finished sub-assemblies are connected in electrical series by interposing connective material between the end surfaces of adjacent cells, whereby individual cells may be inspected for defects and interchanged with non-defective single cell units.

A solvent-free microbial-activated air cathode battery paper platform made with pencil-traced graphite electrodes.

PubMed

Lee, Seung Ho; Ban, Ju Yeon; Oh, Chung-Hun; Park, Hun-Kuk; Choi, Samjin

2016-06-23

We present the fabrication of an ultra-low cost, disposable, solvent-free air cathode all-paper microbial fuel cell (MFC) that does not utilize any chemical treatments. The anode and cathode were fabricated by depositing graphite particles by drawing them on paper with a pencil (four strokes). Hydrophobic parchment paper was used as a proton exchange membrane (PEM) to allow only H(+) to pass. Air cathode MFC technology, where O2 was used as an electron acceptor, was implemented on the paper platform. The bioelectric current was generated by an electrochemical process involving the redox couple of microbial-activated extracellular electron transferred electrons, PEM-passed H(+), and O2 in the cathode. A fully micro-integrated pencil-traced MFC showed a fast start-time, producing current within 10 s after injection of bacterial cells. A single miniaturized all-paper air cathode MFC generated a maximum potential of 300 mV and a maximum current of 11 μA during 100 min after a single injection of Shewanella oneidensis. The micro-fabricated solvent-free air cathode all-paper MFC generated a power of 2,270 nW (5.68 mW/m(2)). The proposed solvent-free air cathode paper-based MFC device could be used for environmentally-friendly energy storage as well as in single-use medical power supplies that use organic matter.

A solvent-free microbial-activated air cathode battery paper platform made with pencil-traced graphite electrodes

PubMed Central

Lee, Seung Ho; Ban, Ju Yeon; Oh, Chung-Hun; Park, Hun-Kuk; Choi, Samjin

2016-01-01

We present the fabrication of an ultra-low cost, disposable, solvent-free air cathode all-paper microbial fuel cell (MFC) that does not utilize any chemical treatments. The anode and cathode were fabricated by depositing graphite particles by drawing them on paper with a pencil (four strokes). Hydrophobic parchment paper was used as a proton exchange membrane (PEM) to allow only H+ to pass. Air cathode MFC technology, where O2 was used as an electron acceptor, was implemented on the paper platform. The bioelectric current was generated by an electrochemical process involving the redox couple of microbial-activated extracellular electron transferred electrons, PEM-passed H+, and O2 in the cathode. A fully micro-integrated pencil-traced MFC showed a fast start-time, producing current within 10 s after injection of bacterial cells. A single miniaturized all-paper air cathode MFC generated a maximum potential of 300 mV and a maximum current of 11 μA during 100 min after a single injection of Shewanella oneidensis. The micro-fabricated solvent-free air cathode all-paper MFC generated a power of 2,270 nW (5.68 mW/m2). The proposed solvent-free air cathode paper-based MFC device could be used for environmentally-friendly energy storage as well as in single-use medical power supplies that use organic matter. PMID:27333815

Improved performance of single-chamber microbial fuel cells through control of membrane deformation.

PubMed

Zhang, Xiaoyuan; Cheng, Shaoan; Huang, Xia; Logan, Bruce E

2010-03-15

Cation (CEMs) and anion exchange membrane (AEMs) are commonly used in microbial fuel cells (MFCs) to enhance Coulombic efficiencies (CEs) by reducing the flux of oxygen through the cathode to bacteria on the anode. AEMs typically work better than CEMs, but in initial experiments we observed the opposite using a membrane electrode assembly MFC. The reason was identified to be membrane deformation, which resulted in water and gas trapped between the membrane and cathode. To correct this, stainless steel mesh was used to press the membrane flat against the cathode. With the steel mesh, AEM performance increased to 46+/-4 W/m(3) in a single cathode MFC, and 98+/-14 W/m(3) in a double-cathode MFC. These power densities were higher than those using a CEM of 32+/-2 W/m(3) (single cathode) and 63+/-6 W/m(3) (double cathode). Higher pH gradients across the membrane and salt precipitation on the cathode were responsible for the reduced performance of the CEM compared to the AEM. CEs reached over 90% for both membranes at >2A/m(2). These results demonstrate the importance of avoiding water accumulation in thin films between membranes and electrodes, and explain additional reasons for poorer performance of CEMs compared to AEMs. (c) 2009 Elsevier B.V. All rights reserved.

A solvent-free microbial-activated air cathode battery paper platform made with pencil-traced graphite electrodes

NASA Astrophysics Data System (ADS)

Lee, Seung Ho; Ban, Ju Yeon; Oh, Chung-Hun; Park, Hun-Kuk; Choi, Samjin

2016-06-01

We present the fabrication of an ultra-low cost, disposable, solvent-free air cathode all-paper microbial fuel cell (MFC) that does not utilize any chemical treatments. The anode and cathode were fabricated by depositing graphite particles by drawing them on paper with a pencil (four strokes). Hydrophobic parchment paper was used as a proton exchange membrane (PEM) to allow only H+ to pass. Air cathode MFC technology, where O2 was used as an electron acceptor, was implemented on the paper platform. The bioelectric current was generated by an electrochemical process involving the redox couple of microbial-activated extracellular electron transferred electrons, PEM-passed H+, and O2 in the cathode. A fully micro-integrated pencil-traced MFC showed a fast start-time, producing current within 10 s after injection of bacterial cells. A single miniaturized all-paper air cathode MFC generated a maximum potential of 300 mV and a maximum current of 11 μA during 100 min after a single injection of Shewanella oneidensis. The micro-fabricated solvent-free air cathode all-paper MFC generated a power of 2,270 nW (5.68 mW/m2). The proposed solvent-free air cathode paper-based MFC device could be used for environmentally-friendly energy storage as well as in single-use medical power supplies that use organic matter.

Oxygen-reducing biocathodes operating with passive oxygen transfer in microbial fuel cells.

PubMed

Xia, Xue; Tokash, Justin C; Zhang, Fang; Liang, Peng; Huang, Xia; Logan, Bruce E

2013-02-19

Oxygen-reducing biocathodes previously developed for microbial fuel cells (MFCs) have required energy-intensive aeration of the catholyte. To avoid the need for aeration, the ability of biocathodes to function with passive oxygen transfer was examined here using air cathode MFCs. Two-chamber, air cathode MFCs with biocathodes produced a maximum power density of 554 ± 0 mW/m(2), which was comparable to that obtained with a Pt cathode (576 ± 16 mW/m(2)), and 38 times higher than that produced without a catalyst (14 ± 3 mW/m(2)). The maximum current density with biocathodes in this air-cathode MFC was 1.0 A/m(2), compared to 0.49 A/m(2) originally produced in a two-chamber MFC with an aqueous cathode (with cathode chamber aeration). Single-chamber, air-cathode MFCs with the same biocathodes initially produced higher voltages than those with Pt cathodes, but after several cycles the catalytic activity of the biocathodes was lost. This change in cathode performance resulted from direct exposure of the cathodes to solutions containing high concentrations of organic matter in the single-chamber configuration. Biocathode performance was not impaired in two-chamber designs where the cathode was kept separated from the anode solution. These results demonstrate that direct-air biocathodes can work very well, but only under conditions that minimize heterotrophic growth of microorganisms on the cathodes.

Effect of thermionic cathode heating current self-magnetic field on gaseous plasma generator characteristics

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

Lopatin, I. V., E-mail: lopatin@opee.hcei.tsc.ru; Akhmadeev, Yu. H.; Koval, N. N.

2015-10-15

The performance capabilities of the PINK, a plasma generator with a thermionic cathode mounted in the cavity of a hollow cathode, depending for its operation on a non-self-sustained low-pressure gas discharge have been investigated. It has been shown that when a single-filament tungsten cathode 2 mm in diameter is used and the peak filament current is equal to or higher than 100 A, the self-magnetic field of the filament current significantly affects the discharge current and voltage waveforms. This effect is due to changes in the time and space distributions of the emission current density from the hot cathode. Whenmore » the electron mean free path is close to the characteristic dimensions of the thermionic cathode, the synthesized plasma density distribution is nonuniform and the cathode is etched nonuniformly. The cathode lifetime in this case is 8–12 h. Using a cathode consisting of several parallel-connected tungsten filaments ∼0.8 mm in diameter moderates the effect of the self-magnetic field of the filament current and nearly doubles the cathode lifetime. The use of this type of cathode together with a discharge igniting electrode reduces the minimum operating pressure in the plasma generator to about one third of that required for the generator operation with a single-filament cathode (to 0.04 Pa)« less

An array of virtual Frisch-grid CdZnTe detectors and a front-end application-specific integrated circuit for large-area position-sensitive gamma-ray cameras.

PubMed

Bolotnikov, A E; Ackley, K; Camarda, G S; Cherches, C; Cui, Y; De Geronimo, G; Fried, J; Hodges, D; Hossain, A; Lee, W; Mahler, G; Maritato, M; Petryk, M; Roy, U; Salwen, C; Vernon, E; Yang, G; James, R B

2015-07-01

We developed a robust and low-cost array of virtual Frisch-grid CdZnTe detectors coupled to a front-end readout application-specific integrated circuit (ASIC) for spectroscopy and imaging of gamma rays. The array operates as a self-reliant detector module. It is comprised of 36 close-packed 6 × 6 × 15 mm(3) detectors grouped into 3 × 3 sub-arrays of 2 × 2 detectors with the common cathodes. The front-end analog ASIC accommodates up to 36 anode and 9 cathode inputs. Several detector modules can be integrated into a single- or multi-layer unit operating as a Compton or a coded-aperture camera. We present the results from testing two fully assembled modules and readout electronics. The further enhancement of the arrays' performance and reduction of their cost are possible by using position-sensitive virtual Frisch-grid detectors, which allow for accurate corrections of the response of material non-uniformities caused by crystal defects.

An array of virtual Frisch-grid CdZnTe detectors and a front-end application-specific integrated circuit for large-area position-sensitive gamma-ray cameras

DOE PAGES

Bolotnikov, A. E.; Ackley, K.; Camarda, G. S.; ...

2015-07-28

We developed a robust and low-cost array of virtual Frisch-grid CdZnTe (CZT) detectors coupled to a front-end readout ASIC for spectroscopy and imaging of gamma rays. The array operates as a self-reliant detector module. It is comprised of 36 close-packed 6x6x15 mm 3 detectors grouped into 3x3 sub-arrays of 2x2 detectors with the common cathodes. The front-end analog ASIC accommodates up to 36 anode and 9 cathode inputs. Several detector modules can be integrated into a single- or multi-layer unit operating as a Compton or a coded-aperture camera. We present the results from testing two fully assembled modules and readoutmore » electronics. The further enhancement of the arrays’ performance and reduction of their cost are made possible by using position-sensitive virtual Frisch-grid detectors, which allow for accurate corrections of the response of material non-uniformities caused by crystal defects.« less

Graphitic biochar as a cathode electrocatalyst support for microbial fuel cells.

PubMed

Huggins, Tyler M; Pietron, Jeremy J; Wang, Heming; Ren, Zhiyong Jason; Biffinger, Justin C

2015-11-01

Graphitic biochar (BC) was generated using high temperature gasification and alkaline post-treatment (BCw) of wood-based biomass. The BCw was evaluated as a manganese oxide electrocatalytic support (MnO/BCw) and microbial fuel cell (MFC) air cathode. Nano-structured MnO2 crystals were successfully immobilized on biomass-based graphitic sheets and characterized using physical, chemical, and electrochemical analyses. Cyclic voltammetry of MnO/BCw/Nafion inks showed electrochemical features typical of β-MnO2 with a current density of 0.9 mA cm(-2). BC showed satisfactory maximum power densities of 146.7 mW m(-2) (BCw) and 187.8 W m(-2) (MnO/BCw), compared with Vulcan Carbon (VC) (156.8 mW m(-2)) and manganese oxide VC composites (MnO/VC) (606.1 mW m(-2)). These materials were also tested as oxygen reduction reaction (ORR) catalysts for single chamber MFCs inoculated with anaerobic sludge. Our results demonstrate that BC can serve as an effective, low cost, and scalable material for MFC application. Published by Elsevier Ltd.

Mesoporous Pd/Co3O4 nanosheets nanoarrays as an efficient binder/carbon free cathode for rechargeable Li-O2 batteries

NASA Astrophysics Data System (ADS)

Ren, Yanbiao; Zhang, Shichao; Li, Honglei; Wei, Xin; Xing, Yanlan

2017-10-01

In this work, two shapes of mesoporous Co3O4 nanoarrays (i.e., nanosheets, nanowires) were synthesized through a facile hydrothermal method on nickel foam (Ni foam) substrates and tested as the Li-O2 cathodes. The comparison of these two shapes of Co3O4 nanoarrays revealed that the single crystalline feature of Co3O4 nanosheets with a predominant high reactivity {112} exposed crystal plane, favorable nanostructure and high specific area displayed better catalytic performance. Furthermore, a new binder/carbon-free Pd nanoparticles (PdNPs) decorated Co3O4 nanosheets cathode was also fabricated through the chemical reduction method. The presence of PdNPs effectively promotes the uniform growth of a fluffy, porous discharge product Li2O2 layer on the surface of Pd/Co3O4 electrode. The Pd/Co3O4 electrode catalyzed Li-O2 battery exhibited a higher specific capacity (1551 mAh g-1 at 50 mA g-1), lower over-potential and longer cycle life over 72 cycles at 100 mA g-1 with the capacity limited at 300 mAh g-1. The superior catalytic performance for Li-O2 batteries is ascribed to the unique design in both component and architecture of Pd/Co3O4 electrode.

Process of electrolysis and fractional crystallization for aluminum purification

DOEpatents

Dawless, R.K.; Bowman, K.A.; Mazgaj, R.M.; Cochran, C.N.

1983-10-25

A method is described for purifying aluminum that contains impurities, the method including the step of introducing such aluminum containing impurities to a charging and melting chamber located in an electrolytic cell of the type having a porous diaphragm permeable by the electrolyte of the cell and impermeable to molten aluminum. The method includes further the steps of supplying impure aluminum from the chamber to the anode area of the cell and electrolytically transferring aluminum from the anode area to the cathode through the diaphragm while leaving impurities in the anode area, thereby purifying the aluminum introduced into the chamber. The method includes the further steps of collecting the purified aluminum at the cathode, and lowering the level of impurities concentrated in the anode area by subjecting molten aluminum and impurities in said chamber to a fractional crystallization treatment wherein eutectic-type impurities crystallize and precipitate out of the aluminum. The eutectic impurities that have crystallized are physically removed from the chamber. The aluminum in the chamber is now suited for further purification as provided in the above step of electrolytically transferring aluminum through the diaphragm. 2 figs.

Process of electrolysis and fractional crystallization for aluminum purification

DOEpatents

Dawless, Robert K.; Bowman, Kenneth A.; Mazgaj, Robert M.; Cochran, C. Norman

1983-10-25

A method for purifying aluminum that contains impurities, the method including the step of introducing such aluminum containing impurities to a charging and melting chamber located in an electrolytic cell of the type having a porous diaphragm permeable by the electrolyte of the cell and impermeable to molten aluminum. The method includes further the steps of supplying impure aluminum from the chamber to the anode area of the cell and electrolytically transferring aluminum from the anode area to the cathode through the diaphragm while leaving impurities in the anode area, thereby purifying the aluminum introduced into the chamber. The method includes the further steps of collecting the purified aluminum at the cathode, and lowering the level of impurities concentrated in the anode area by subjecting molten aluminum and impurities in said chamber to a fractional crystallization treatment wherein eutectic-type impurities crystallize and precipitate out of the aluminum. The eutectic impurities that have crystallized are physically removed from the chamber. The aluminum in the chamber is now suited for further purification as provided in the above step of electrolytically transferring aluminum through the diaphragm.

Pseudocapacitive Sodium Storage in Mesoporous Single-Crystal-like TiO2-Graphene Nanocomposite Enables High-Performance Sodium-Ion Capacitors.

PubMed

Le, Zaiyuan; Liu, Fang; Nie, Ping; Li, Xinru; Liu, Xiaoyan; Bian, Zhenfeng; Chen, Gen; Wu, Hao Bin; Lu, Yunfeng

2017-03-28

Sodium-ion capacitors can potentially combine the virtues of high power capability of conventional electrochemical capacitors and high energy density of batteries. However, the lack of high-performance electrode materials has been the major challenge of sodium-based energy storage devices. In this work, we report a microwave-assisted synthesis of single-crystal-like anatase TiO 2 mesocages anchored on graphene as a sodium storage material. The architecture of the nanocomposite results in pseudocapacitive charge storage behavior with fast kinetics, high reversibility, and negligible degradation to the micro/nanostructure. The nanocomposite delivers a high capacity of 268 mAh g -1 at 0.2 C, which remains 126 mAh g -1 at 10 C for over 18 000 cycles. Coupling with a carbon-based cathode, a full cell of sodium-ion capacitor successfully demonstrates a high energy density of 64.2 Wh kg -1 at 56.3 W kg -1 and 25.8 Wh kg -1 at 1357 W kg -1 , as well as an ultralong lifespan of 10 000 cycles with over 90% of capacity retention.

Semiconductor crystal high resolution imager

NASA Technical Reports Server (NTRS)

Matteson, James (Inventor); Levin, Craig S. (Inventor)

2011-01-01

A radiation imaging device (10). The radiation image device (10) comprises a subject radiation station (12) producing photon emissions (14), and at least one semiconductor crystal detector (16) arranged in an edge-on orientation with respect to the emitted photons (14) to directly receive the emitted photons (14) and produce a signal. The semiconductor crystal detector (16) comprises at least one anode and at least one cathode that produces the signal in response to the emitted photons (14).

High voltage photovoltaic power converter

DOEpatents

Haigh, Ronald E.; Wojtczuk, Steve; Jacobson, Gerard F.; Hagans, Karla G.

2001-01-01

An array of independently connected photovoltaic cells on a semi-insulating substrate contains reflective coatings between the cells to enhance efficiency. A uniform, flat top laser beam profile is illuminated upon the array to produce electrical current having high voltage. An essentially wireless system includes a laser energy source being fed through optic fiber and cast upon the photovoltaic cell array to prevent stray electrical signals prior to use of the current from the array. Direct bandgap, single crystal semiconductor materials, such as GaAs, are commonly used in the array. Useful applications of the system include locations where high voltages are provided to confined spaces such as in explosive detonation, accelerators, photo cathodes and medical appliances.

Synthesis of three-dimensionally interconnected sulfur-rich polymers for cathode materials of high-rate lithium-sulfur batteries

NASA Astrophysics Data System (ADS)

Kim, Hoon; Lee, Joungphil; Ahn, Hyungmin; Kim, Onnuri; Park, Moon Jeong

2015-06-01

Elemental sulfur is one of the most attractive cathode active materials in lithium batteries because of its high theoretical specific capacity. Despite the positive aspect, lithium-sulfur batteries have suffered from severe capacity fading and limited rate capability. Here we report facile large-scale synthesis of a class of organosulfur compounds that could open a new chapter in designing cathode materials to advance lithium-sulfur battery technologies. Porous trithiocyanuric acid crystals are synthesized for use as a soft template, where the ring-opening polymerization of elemental sulfur takes place along the thiol surfaces to create three-dimensionally interconnected sulfur-rich phases. Our lithium-sulfur cells display discharge capacity of 945 mAh g-1 after 100 cycles at 0.2 C with high-capacity retention of 92%, as well as lifetimes of 450 cycles. Particularly, the organized amine groups in the crystals increase Li+-ion transfer rate, affording a rate performance of 1210, mAh g-1 at 0.1 C and 730 mAh g-1 at 5 C.

Synthesis of three-dimensionally interconnected sulfur-rich polymers for cathode materials of high-rate lithium–sulfur batteries

PubMed Central

Kim, Hoon; Lee, Joungphil; Ahn, Hyungmin; Kim, Onnuri; Park, Moon Jeong

2015-01-01

Elemental sulfur is one of the most attractive cathode active materials in lithium batteries because of its high theoretical specific capacity. Despite the positive aspect, lithium–sulfur batteries have suffered from severe capacity fading and limited rate capability. Here we report facile large-scale synthesis of a class of organosulfur compounds that could open a new chapter in designing cathode materials to advance lithium–sulfur battery technologies. Porous trithiocyanuric acid crystals are synthesized for use as a soft template, where the ring-opening polymerization of elemental sulfur takes place along the thiol surfaces to create three-dimensionally interconnected sulfur-rich phases. Our lithium–sulfur cells display discharge capacity of 945 mAh g−1 after 100 cycles at 0.2 C with high-capacity retention of 92%, as well as lifetimes of 450 cycles. Particularly, the organized amine groups in the crystals increase Li+-ion transfer rate, affording a rate performance of 1210, mAh g−1 at 0.1 C and 730 mAh g−1 at 5 C. PMID:26065407

Li 3Mo 4P 5O 24: A two-electron cathode for lithium-ion batteries with three-dimensional diffusion pathways

DOE PAGES

Wen, Bohua; Khalifah, Peter G.; Liu, Jue; ...

2016-04-12

The structure of the novel compound Li 3Mo 4P 5O 24 has been solved from single crystal X-ray diffraction data. The Mo cations in Li 3Mo 4P 5O 24 are present in four distinct types of MoO 6 octahedra, each of which has one open vertex at the corner participating in a Mo=O double bond and whose other five corners are shared with PO 4 tetrahedra. On the basis of a bond valence sum difference map (BVS-DM) analysis, this framework is predicted to support the facile diffusion of Li + ions, a hypothesis that is confirmed by electrochemical testing data,more » which show that Li 3Mo 4P 5O 24 can be utilized as a rechargeable battery cathode material. It is found that Li can both be removed from and inserted into Li 3Mo 4P 5O 24. The involvement of multiple redox processes occurring at the same Mo site is reflected in electrochemical plateaus around 3.8 V associated with the Mo 6+/Mo 5+ redox couple and 2.2 V associated with the Mo 5+/Mo 4+ redox couple. The two-electron redox properties of Mo cations in this structure lead to a theoretical capacity of 198 mAh/g. When cycled between 2.0 and 4.3 V versus Li +/Li, an initial capacity of 113 mAh/g is observed with 80% of this capacity retained over the first 20 cycles. Lastly, this compound therefore represents a rare example of a solid state cathode able to support two-electron redox capacity and provides important general insights about pathways for designing next-generation cathodes with enhanced specific capacities.« less

Arrays of Position-Sensitive Virtual Frisch-Grid CdZnTe Detectors: Results From a $$4\\times 4$$ Array Prototype

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

Ocampo Giraldo, L. A.; Bolotnikov, A. E.; Camarda, G. S.

Position-sensitive virtual Frisch-grid (VFG) CdZnTe (CZT) detectors offer a unique capability for correcting the response nonuniformities caused by crystal defects. This allowed us to achieve high energy resolution, while using typical-grade commercial CZT crystals with relaxed requirements to their quality, thus reducing the overall cost of detectors. Another advantage of the VFG detectors is that they can be integrated into arrays and used in small compact hand-held instruments or large-area gamma cameras that will enhance detection capability for many practical applications, including nonproliferation, medical imaging, and gamma-ray astronomy. Here in this paper, we present the results from testing small arraymore » prototypes coupled with front-end application-specified integrated circuit. Each detector in the array is furnished with 5-mm-wide charge-sensing pads placed near the anode. The pads signals are converted into XY coordinates, which combined with the cathode signals (for Z coordinates) provide 3-D position information of all interaction points. The basic array consists of a number of detectors grouped into 2×2 subarrays, each having a common cathode made by connecting together the cathodes of the individual detectors. Lastly, these features can significantly improve the performance of detectors while using typical-grade low-cost CZT crystals to reduce the overall cost of the proposed instrument.« less

Arrays of Position-Sensitive Virtual Frisch-Grid CdZnTe Detectors: Results From a $$4\\times 4$$ Array Prototype

DOE PAGES

Ocampo Giraldo, L. A.; Bolotnikov, A. E.; Camarda, G. S.; ...

2017-08-22

Position-sensitive virtual Frisch-grid (VFG) CdZnTe (CZT) detectors offer a unique capability for correcting the response nonuniformities caused by crystal defects. This allowed us to achieve high energy resolution, while using typical-grade commercial CZT crystals with relaxed requirements to their quality, thus reducing the overall cost of detectors. Another advantage of the VFG detectors is that they can be integrated into arrays and used in small compact hand-held instruments or large-area gamma cameras that will enhance detection capability for many practical applications, including nonproliferation, medical imaging, and gamma-ray astronomy. Here in this paper, we present the results from testing small arraymore » prototypes coupled with front-end application-specified integrated circuit. Each detector in the array is furnished with 5-mm-wide charge-sensing pads placed near the anode. The pads signals are converted into XY coordinates, which combined with the cathode signals (for Z coordinates) provide 3-D position information of all interaction points. The basic array consists of a number of detectors grouped into 2×2 subarrays, each having a common cathode made by connecting together the cathodes of the individual detectors. Lastly, these features can significantly improve the performance of detectors while using typical-grade low-cost CZT crystals to reduce the overall cost of the proposed instrument.« less

Dual functions of zirconium modification on improving the electrochemical performance of Ni-rich LiNi0.8Co0.1Mn0.1O2

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

Li, Xing; Zhang, Kangjia; Wang, Mingshan

2018-02-28

Trace amount of Zirconium (Zr) has been adopted to modify the crystal structure and surface of the Ni-rich LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode material. During cycling at 1.0C, the Zr-modified NCM811 shows an improved capacity retention of 92% after 100 cycles, higher than 75% for pristine NMC811. In addition, the Zr-modified NCM811 is capable of delivering a discharge capacity of 107 mAh g-1 at 10.0C rate, much higher than 28 mAh g-1 delivered by pristine material. These improved electrochemical performances are ascribed to the dual functions of Zr modification. On one hand, part of the Zr enters the crystal lattice, which ismore » beneficial for reducing the Li/Ni cation mixing and enhancing the crystal stability of the cathode. On the other hand, the rest of the Zr forms a 1~2 nm thick coating layer on the surface of the NCM811 cathode, which effectively prevents the direct contact between NCM and the electrolyte, thus suppressing the detrimental interfacial reactions. Therefore, the Zr-modified LiNi0.8Co0.1Mn0.1O2 exhibited significantly enhanced cycling stability and charging/discharging rate capability in comparison with the untreated counterpart.« less

Improved electrochemical property of nanoparticle polyoxovanadate K7NiV13O38 as cathode material for lithium battery

NASA Astrophysics Data System (ADS)

Ni, Erfu; Uematsu, Shinya; Quan, Zhen; Sonoyama, Noriyuki

2013-06-01

Molecular cluster ion compound K7NiV13O38 (KNiV) has been studied as a novel cathode material for lithium ion battery. The nanoparticles are prepared by a simple re-crystallization method adding different volumes of acetone to the water solution containing the dissolved KNiV. The KNiV re-crystallized from water/acetone ratio of 1:5 shows the most uniform particle size distribution and the smallest particles with thickness of 100 nm and width of 150 nm. The nanoparticle KNiV shows significant improvement in initial discharge capacity and capacity retention after 50 cycles compared to the as-prepared micro-sized particles at various current densities. Ex situ XRD patterns demonstrate that the discharge-charge process proceeds with amorphous KNiV, which is independent from the crystal structure. Ex situ FT-IR spectra indicate that [NiV13O38]7- cluster ion is stable and reacts reversibly with lithium ion in the discharge-charge process.

Structural, optical and electrical properties of CeO2 thin films simultaneously prepared by anodic and cathodic electrodeposition

NASA Astrophysics Data System (ADS)

Yang, Yumeng; Du, Xiaoqing; Yi, Chenxi; Liu, Jiao; Zhu, Benfeng; Zhang, Zhao

2018-05-01

CeO2 thin films were deposited on stainless steel (SS) and indium tin oxide (ITO)-coated glass by simultaneous anodic and cathodic electrodeposition, and the influence of negative potential on the formation of ceria films was studied with scanning electron microscopy, X-ray diffraction, Raman spectroscopy, van der Pauw measurements, UV-visible spectroscopy and X-ray photoelectron spectroscopy. The results show that CeO2 films on the anode are slightly affected by the potential, but the particle size, crystal orientation, strain, film thickness, resistivity and Ce(III) content of the films on the cathode increases with increasing potential on the SS substrate. Contradictory to the results of the SS cathode, redshift (Ed changed from 3.95 eV to 3.56 eV and Ei changed from 3.42 eV to 3.04 eV) occurring in the absorption spectrum of CeO2 deposited on the ITO-coated glass cathode indicates that the content of Ce3+ in the cathodic films is dependent on the adopted substrates and decreases as the applied potential is increased.

Lattice-cell orientation disorder in complex spinel oxides

DOE PAGES

Chen, Yan; Cheng, Yongqiang; Li, Juchuan; ...

2016-11-07

Transition metal (TM) substitution has been widely applied to change complex oxides crystal structures to create high energy density electrodes materials in high performance rechargeable lithium-ion batteries. The complex local structure in the oxides imparted by the TM arrangement often impacts their electrochemical behaviors by influencing the diffusion and intercalation of lithium. Here, a major discrepancy is demonstrated between the global and local structures of the promising high energy density and high voltage LiNi 0.5Mn 1.5O 4 spinel cathode material that contradicts the existing structural models. A new single-phase lattice-cell orientation disorder model is proposed as the mechanism for themore » local ordering that explains how the inhomogeneous local distortions and the coherent connection give rise to the global structure in the complex oxide. As a result, the single-phase model is consistent with the electrochemical behavior observation of the materials.« less

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

Chen, Yan; Cheng, Yongqiang; Li, Juchuan

Transition metal (TM) substitution has been widely applied to change complex oxides crystal structures to create high energy density electrodes materials in high performance rechargeable lithium-ion batteries. The complex local structure in the oxides imparted by the TM arrangement often impacts their electrochemical behaviors by influencing the diffusion and intercalation of lithium. Here, a major discrepancy is demonstrated between the global and local structures of the promising high energy density and high voltage LiNi 0.5Mn 1.5O 4 spinel cathode material that contradicts the existing structural models. A new single-phase lattice-cell orientation disorder model is proposed as the mechanism for themore » local ordering that explains how the inhomogeneous local distortions and the coherent connection give rise to the global structure in the complex oxide. As a result, the single-phase model is consistent with the electrochemical behavior observation of the materials.« less

Investigation of materials for inert electrodes in aluminum electrodeposition cells

NASA Astrophysics Data System (ADS)

Haggerty, J. S.; Sadoway, D. R.

1987-09-01

Work was divided into major efforts. The first was the growth and characterization of specimens; the second was Hall cell performance testing. Cathode and anode materials were the subject of investigation. Preparation of specimens included growth of single crystals and synthesis of ultra high purity powders. Special attention was paid to ferrites as they were considered to be the most promising anode materials. Ferrite anode corrosion rates were studied and the electrical conductivities of a set of copper-manganese ferrites were measured. Float Zone, Pendant Drop Cryolite Experiments were undertaken because unsatisfactory choices of candidate materials were being made on the basis of a flawed set of selection criteria applied to an incomplete and sometimes inaccurate data base. This experiment was then constructed to determine whether the apparatus used for float zone crystal growth could be adapted to make a variety of important based melts and their interactions with candidate inert anode materials. Compositions), driven by our perception that the basis for prior selection of candidate materials was inadequate. Results are presented.

Solid oxide fuel cell with multi-unit construction and prismatic design

DOEpatents

McPheeters, C.C.; Dees, D.W.; Myles, K.M.

1999-03-16

A single cell unit of a solid oxide fuel cell is described that is individually fabricated and sintered prior to being connected to adjacent cells to form a solid oxide fuel cell. The single cell unit is comprised of a shaped anode sheet positioned between a flat anode sheet and an anode-electrolyte-cathode (A/E/C) sheet, and a shaped cathode sheet positioned between the A/E/C sheet and a cathode-interconnect-anode (C/I/A) sheet. An alternate embodiment comprises a shaped cathode sheet positioned between an A/E/C sheet and a C/I/A sheet. The shaped sheets form channels for conducting reactant gases. Each single cell unit is individually sintered to form a finished sub-assembly. The finished sub-assemblies are connected in electrical series by interposing connective material between the end surfaces of adjacent cells, whereby individual cells may be inspected for defects and interchanged with non-defective single cell units. 7 figs.

Cathodic and anodic biofilms in Single Chamber Microbial Fuel Cells.

PubMed

Cristiani, P; Carvalho, M L; Guerrini, E; Daghio, M; Santoro, C; Li, B

2013-08-01

The oxygen reduction due to microaerophilic biofilms grown on graphite cathodes (biocathodes) in Single Chamber Microbial Fuel Cells (SCMFCs) is proved and analysed in this paper. Pt-free cathode performances are compared with those of different platinum-loaded cathodes, before and after the biofilm growth. Membraneless SCMFCs were operating in batch-mode, filled with wastewater. A substrate (fuel) of sodium acetate (0.03 M) was periodically added and the experiment lasted more than six months. A maximum of power densities, up to 0.5 W m(-2), were reached when biofilms developed on the electrodes and the cathodic potential decreased (open circuit potential of 50-200 mV vs. SHE). The power output was almost constant with an acetate concentration of 0.01-0.05 M and it fell down when the pH of the media exceeded 9.5, independently of the Pt-free/Pt-loading at the cathodes. Current densities varied in the range of 1-5 Am(-2) (cathode area of 5 cm(2)). Quasi-stationary polarization curves performed with a three-electrode configuration on cathodic and anodic electrodes showed that the anodic overpotential, more than the cathodic one, may limit the current density in the SCMFCs for a long-term operation. Copyright © 2012 Elsevier B.V. All rights reserved.

Pure Single-Crystalline Na1.1V3O7.9 Nanobelts as Superior Cathode Materials for Rechargeable Sodium-Ion Batteries.

PubMed

Yuan, Shuang; Liu, Yong-Bing; Xu, Dan; Ma, De-Long; Wang, Sai; Yang, Xiao-Hong; Cao, Zhan-Yi; Zhang, Xin-Bo

2015-03-01

Pure single-crystalline Na 1.1 V 3 O 7.9 nanobelts are successfully synthesized for the first time via a facile yet effective strategy. When used as cathode materials for Na-ion batteries, the novel nanobelts exhibit excellent electrochemical performance. Given the ease and effectiveness of the synthesis route as well as the very promising electrochemical performance, the results obtained may be extended to other next-generation cathode materials for Na-ion batteries.

Cobalt porphyrin-based material as methanol tolerant cathode in single chamber microbial fuel cells (SCMFCs)

NASA Astrophysics Data System (ADS)

Liu, Bingchuan; Brückner, Cristian; Lei, Yu; Cheng, Yue; Santoro, Carlo; Li, Baikun

2014-07-01

This study focused on the development of novel cathode material based on the pyrolysis of [meso-tetrakis(2-thienyl)porphyrinato]Co(II) (CoTTP) for use in single chamber microbial fuel cells (SCMFCs) to treat wastewater containing methanol. The cathodes produced at two loadings (0.5 and 1.0 mg cm-2) were examined in batch mode SCMFCs treating methanol of different concentrations (ranging from 0.005 to 0.04 M) over a 900 h operational period. Methanol was completely removed in SCMFCs, and the cycle duration was prolonged at high methanol concentrations, indicating methanol was used as fuel in SCMFCs. Methanol had more poisoning effects to the traditional platinum (Pt) cathodes than to the CoTTP cathodes. Specifically, power generations from SCMFCs with Pt cathodes gradually decreased over time, while the ones with CoTTP cathodes remained stable, even at the highest methanol concentration (0.04 M). Cathode linear sweep voltammetry (LSVs) indicated that the electrocatalytic activity of the Pt cathode was suppressed by methanol. Higher CoTTP loadings had similar open circuit potential (OCP) but higher electrocatalytic activity than lower loadings. This study demonstrated that methanol can be co-digested with wastewater and converted to power in MFCs, and a novel cathode CoTTP catalyst exhibits higher tolerance towards methanol compared with traditional Pt catalyst.

Sub-2 nm Thick Fluoroalkylsilane Self-Assembled Monolayer-Coated High Voltage Spinel Crystals as Promising Cathode Materials for Lithium Ion Batteries

PubMed Central

Zettsu, Nobuyuki; Kida, Satoru; Uchida, Shuhei; Teshima, Katsuya

2016-01-01

We demonstrate herein that an ultra-thin fluoroalkylsilane self-assembled monolayer coating can be used as a modifying agent at LiNi0.5Mn1.5O4−δcathode/electrolyte interfaces in 5V-class lithium-ion batteries. Bare LiNi0.5Mn1.5O4−δ cathode showed substantial capacity fading, with capacity dropping to 79% of the original capacity after 100 cycles at a rate of 1C, which was entirely due to dissolution of Mn3+ from the spinel lattice via oxidative decomposition of the organic electrolyte. Capacity retention was improved to 97% on coating ultra-thin FAS17-SAM onto the LiNi0.5Mn1.5O4 cathode surface. Such surface protection with highly ordered fluoroalkyl chains insulated the cathode from direct contact with the organic electrolyte and led to increased tolerance to HF. PMID:27553901

Cataphoretic assembly of cationic dyes and deposition of carbon nanotube and graphene films.

PubMed

Su, Y; Zhitomirsky, I

2013-06-01

Cathodic electrophoretic deposition (EPD) method has been developed for the fabrication of thin films from aqueous solutions of crystal violet (CV) dyes. The films contained rod-like particles with a long axis oriented perpendicular to the substrate surface. The proposed deposition mechanism involved cataphoresis of cationic CV(+) species, base generation in the cathodic reactions, and charge neutralization at the electrode surface. The assembly of rod-like particles was governed by π-π interactions of polyaromatic CV molecules. The deposition kinetics was studied by quartz crystal microbalance. CV dyes allowed efficient dispersion of multiwalled carbon nanotubes (MWCNTs) and graphene in water at relatively low CV concentrations. The feasibility of cathodic EPD of MWCNT and graphene from aqueous suspensions, containing CV, has been demonstrated. The deposition yield was investigated at different CV concentrations and deposition voltages. The relatively high deposition yield of MWCNT and graphene indicated that CV is an efficient dispersing, charging, and film forming agent for EPD. Electron microscopy data showed that at low CV concentrations in MWCNT or graphene suspensions and low deposition voltages, the films contained mainly MWCNT or graphene. The increase in the CV concentration and/or deposition voltage resulted in enhanced co-deposition of CV. The EPD method developed in this investigation paves the way for the fabrication of advanced nanocomposites by cathodic electrodeposition. Copyright © 2013 Elsevier Inc. All rights reserved.

Advances in electrometer vacuum tube design

NASA Technical Reports Server (NTRS)

1970-01-01

Single-ended, miniature-cathode tube with a relatively low grid current level is constructed. Adequate cathode temperature at relatively low heater power drain is provided by designing the supporting spacers to provide a square cathode hole. Method of assembling the mount and bonding the elements is discussed.

Crystal Structure and Transport Properties of Oxygen-Deficient Perovskite Sr 0.9Y 0.1CoO 3-δ

DOE PAGES

Yang, Tianrang; Mattick, Victoria F.; Chen, Yan; ...

2018-01-29

The present work reports a systematic study on temperature-dependent local crystal structure, oxygen stoichiometry, and electrical/electrochemical properties of an oxygen-deficient Sr 0.9Y 0.1CoO 3-δ (SYC10) perovskite using variable-temperature neutron diffraction (VTND), thermal gravimetric analysis, and electrical/electrochemical methods, respectively. The VTND reveals that the crystal symmetry of SYC10 remains P4/mmm tetragonal up to 900 °C. The tetragonal symmetry reflects the net effects of temperature and oxygen stoichiometry on crystal symmetry. The observed p-type electronic conductivity behavior originates from the charge-ordering between the two distinctive Co-sites. The partial oxide-ion conductivity and diffusivity obtained from oxygen permeation measurements are 2.3 × 10 –2more » S cm –1 and 7.98 × 10–8 cm 2/s at 800 °C in air, respectively. The electrochemical oxygen reduction reaction kinetics of the SYC10 cathode is primarily limited by the charge-transfer process at low temperatures (600–650 °C) and oxide-ion migration from the cathode into the electrolyte at high temperatures (700–800 °C).« less

Crystal Structure and Transport Properties of Oxygen-Deficient Perovskite Sr 0.9Y 0.1CoO 3-δ

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

Yang, Tianrang; Mattick, Victoria F.; Chen, Yan

The present work reports a systematic study on temperature-dependent local crystal structure, oxygen stoichiometry, and electrical/electrochemical properties of an oxygen-deficient Sr 0.9Y 0.1CoO 3-δ (SYC10) perovskite using variable-temperature neutron diffraction (VTND), thermal gravimetric analysis, and electrical/electrochemical methods, respectively. The VTND reveals that the crystal symmetry of SYC10 remains P4/mmm tetragonal up to 900 °C. The tetragonal symmetry reflects the net effects of temperature and oxygen stoichiometry on crystal symmetry. The observed p-type electronic conductivity behavior originates from the charge-ordering between the two distinctive Co-sites. The partial oxide-ion conductivity and diffusivity obtained from oxygen permeation measurements are 2.3 × 10 –2more » S cm –1 and 7.98 × 10–8 cm 2/s at 800 °C in air, respectively. The electrochemical oxygen reduction reaction kinetics of the SYC10 cathode is primarily limited by the charge-transfer process at low temperatures (600–650 °C) and oxide-ion migration from the cathode into the electrolyte at high temperatures (700–800 °C).« less

Voltage instability in a simulated fuel cell stack correlated to cathode water accumulation

NASA Astrophysics Data System (ADS)

Owejan, J. P.; Trabold, T. A.; Gagliardo, J. J.; Jacobson, D. L.; Carter, R. N.; Hussey, D. S.; Arif, M.

Single fuel cells running independently are often used for fundamental studies of water transport. It is also necessary to assess the dynamic behavior of fuel cell stacks comprised of multiple cells arranged in series, thus providing many paths for flow of reactant hydrogen on the anode and air (or pure oxygen) on the cathode. In the current work, the flow behavior of a fuel cell stack is simulated by using a single-cell test fixture coupled with a bypass flow loop for the cathode flow. This bypass simulates the presence of additional cells in a stack and provides an alternate path for airflow, thus avoiding forced convective purging of cathode flow channels. Liquid water accumulation in the cathode is shown to occur in two modes; initially nearly all the product water is retained in the gas diffusion layer until a critical saturation fraction is reached and then water accumulation in the flow channels begins. Flow redistribution and fuel cell performance loss result from channel slug formation. The application of in-situ neutron radiography affords a transient correlation of performance loss to liquid water accumulation. The current results identify a mechanism whereby depleted cathode flow on a single cell leads to performance loss, which can ultimately cause an operating proton exchange membrane fuel cell stack to fail.

Effect of cathode shape on vertical buffered electropolishing for niobium SRF cavities

NASA Astrophysics Data System (ADS)

Jin, S.; Wu, A. T.; Lu, X. Y.; Rimmer, R. A.; Lin, L.; Zhao, K.; Mammosser, J.; Gao, J.

2013-09-01

This paper reports the research results of the effect of cathode shape during vertical buffered electropolishing (BEP) by employing a demountable single cell niobium (Nb) superconducting radio frequency (SRF) cavity. Several different cathode shapes such as, for instance, bar, ball, ellipsoid, and wheels of different diameters have been tested. Detailed electropolishing parameters including I-V characteristic, removal rate, surface roughness, and polishing uniformity at different locations inside the demountable cavity are measured. Similar studies are also done on conventional electropolishing (EP) for comparison. It is revealed that cathode shape has dominant effects for BEP especially on the obtaining of a suitable polishing condition and a uniform polishing rate in an Nb SRF single cell cavity. EP appears to have the same tendency. This paper demonstrates that a more homogeneous polishing result can be obtained by optimizing the electric field distribution inside the cavity through the modification of the cathode shape given the conditions that temperature and electrolyte flow are kept constant. Electric field distribution and electrolyte flow patterns inside the cavity are simulated via Poisson-Superfish and Solidworks respectively. With the optimal cathode shape, BEP shows a much faster polishing rate of ∼2.5 μm/min and is able to produce a smoother surface finish in the treatments of single cell cavities in comparison with EP.

Single-ring magnetic cusp low gas pressure ion source

DOEpatents

Bacon, Frank M.; Brainard, John P.; O'Hagan, James B.; Walko, Robert J.

1985-01-01

A single-ring magnetic cusp low gas pressure ion source designed for use in a sealed, nonpumped neutron generator utilizes a cathode and an anode, three electrically floating electrodes (a reflector behind the cathode, a heat shield around the anode, and an aperture plate), together with a single ring-cusp magnetic field, to establish and energy-filtering mechanism for producing atomic-hydrogen ions.

Boron Substituted Na 3 V 2 (P 1 -x B x O 4 ) 3 Cathode Materials with Enhanced Performance for Sodium-Ion Batteries

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

Hu, Pu; Wang, Xiaofang; Wang, Tianshi

The development of excellent performance of Na-ion batteries remains great challenge owing to the poor stability and sluggish kinetics of cathode materials. Herein, B substituted Na 3V 2P 3–xB xO 12 (0 ≤ x ≤ 1) as stable cathode materials for Na-ion battery is presented. A combined experimental and theoretical investigations on Na 3V 2P 3–xB xO 12 (0 ≤ x ≤ 1) are undertaken to reveal the evolution of crystal and electronic structures and Na storage properties associated with various concentration of B. X-ray diffraction results indicate that the crystal structure of Na 3V 2P 3–xB xO 12 (0more » ≤ x ≤ 1/3) consisted of rhombohedral Na 3V 2(PO 4) 3 with tiny shrinkage of crystal lattice. X-ray absorption spectra and the calculated crystal structures all suggest that the detailed local structural distortion of substituted materials originates from the slight reduction of V–O distances. Na 3V 2P 3-1/6B 1/6O 12 significantly enhances the structural stability and electrochemical performance, giving remarkable enhanced capacity of 100 and 70 mAh g -1 when the C-rate increases to 5 C and 10 C. Spin-polarized density functional theory (DFT) calculation reveals that, as compared with the pristine Na 3V 2(PO 4) 3, the superior electrochemical performance of the substituted materials can be attributed to the emergence of new boundary states near the band gap, lower Na + diffusion energy barriers, and higher structure stability.« less

A highly active hybrid catalyst modified (La0.60Sr0.40)0.95Co0.20Fe0.80O3-δ cathode for proton conducting solid oxide fuel cells

NASA Astrophysics Data System (ADS)

Lei, Libin; Tao, Zetian; Hong, Tao; Wang, Xiaoming; Chen, Fanglin

2018-06-01

The sluggish reaction kinetics in the cathode usually leads to considerable cathode polarization resistance, hindering the development of proton conducting solid oxide fuel cells (H-SOFCs) operated at intermediate temperatures (400-650 °C). To address this problem, for the first time, a novel hybrid catalyst consisting of PrNi0.5Mn0.5O3 and PrOx is impregnated in the (La0.60Sr0.40)0.95Co0.20Fe0.80O3-δ (LSCF) cathode of H-SOFCs, resulting in significant enhancement of the cathode reaction kinetics. Single cells with impregnated LSCF cathode and BaZr0.8Y0.2O3 (BZY) electrolyte yield a maximum power density (MPD) of 0.198 W cm-2 at 600 °C, more than doubled of that with blank LSCF cathode (0.083 W cm-2). ECR and EIS studies reveal that the hybrid catalyst can substantially accelerate the oxygen-ion transfer and oxygen dissociation-absorption processes in the cathode, resulting in significantly lower polarization resistance and higher MPD. In addition, the hybrid catalyst possesses good chemical and microstructural stability at 600 °C. Consequently, the single cells with impregnated LSCF cathode show excellent durability. This study shows that the impregnation of this novel hybrid catalyst in the cathode could be a promising approach to improve the performance and stability of H-SOFCs.

Comparative study on power generation of dual-cathode microbial fuel cell according to polarization methods.

PubMed

Lee, Kang-yu; Ryu, Wyan-seuk; Cho, Sung-il; Lim, Kyeong-ho

2015-11-01

Microbial fuel cells (MFCs) exist in various forms depending on the type of pollutant to be removed and the expected performance. Dual-cathode MFCs, with their simple structure, are capable of removing both organic matter and nitrogen. Moreover, various methods are available for the collection of polarization data, which can be used to calculate the maximum power density, an important factor of MFCs. Many researchers prefer the method of varying the external resistance in a single-cycle due to the short measurement time and high accuracy. This study compared power densities of dual-cathode MFCs in a single-cycle with values calculated over multi-cycles to determine the optimal polarization method. External resistance was varied from high to low and vice versa in the single-cycle, to calculate power density. External resistance was organized in descending order with initial start-up at open circuit voltage (OCV), and then it was organized in descending order again after the initial start-up at 1000 Ω. As a result, power density was underestimated at the anoxic cathode when the external resistance was varied from low to high, and overestimated at the aerobic cathode and anoxic cathode when external resistance at OCV was reduced following initial start-up. In calculating the power densities of dual-cathode MFCs, this paper recommends the method of gradually reducing the external resistance after initial start-up with high external resistance. Copyright © 2015 Elsevier Ltd. All rights reserved.

Self-aligned gated field emission devices using single carbon nanofiber cathodes

NASA Astrophysics Data System (ADS)

Guillorn, M. A.; Melechko, A. V.; Merkulov, V. I.; Hensley, D. K.; Simpson, M. L.; Lowndes, D. H.

2002-11-01

We report on the fabrication and operation of integrated gated field emission devices using single vertically aligned carbon nanofiber (VACNF) cathodes where the gate aperture has been formed using a self-aligned technique based on chemical mechanical polishing. We find that this method for producing gated cathode devices easily achieves structures with gate apertures on the order of 2 mum that show good concentric alignment to the VACNF emitter. The operation of these devices was explored and field emission characteristics that fit well to the Fowler-Nordheim model of emission was demonstrated.

Effect of overcharge on Li(Ni 0.5Mn 0.3Co 0.2)O 2/graphite lithium ion cells with poly(vinylidene fluoride) binder. III — Chemical changes in the cathode

DOE PAGES

Bareno, Javier; Dietz Rago, Nancy; Dogan, Fulya; ...

2018-01-17

Here, 1.5 Ah pouch cells based on Li(Ni 0.5Mn 0.3Co 0.2)O 2 cathodes and graphite anodes, both containing poly (vinylidene fluoride) (PVDF) binders, were systematically overcharged to 100, 120, 140, 160, 180, and 250% state of charge (SOC), at which point they vented. The cells were subsequently discharged to 0% SOC and disassembled under an inert atmosphere for characterization. A combination of X-ray photoelectron spectroscopy (XPS), scanning-electron microscopy (SEM), energy-dispersive spectroscopy (EDS), 6Li SSNMR, and X-ray diffraction (XRD) analysis of the NMC532 cathodes indicates the formation of a thin C- and O-rich cathode electrolyte interphase layer, progressive Li lossmore » above 140% SOC, and retention of the bulk crystal structure at all states of charge.« less

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

Xu, Yun; Zhao, Mingyang; Khalid, Syed

The high voltage cathode material, LiMn 1.6Ni 0.4O 4, was prepared by a polymer-assisted method. The novelty of this paper is the substitution of Ni with Mn, which already exists in the crystal structure instead of other isovalent metal ion dopants which would result in capacity loss. The electrochemical performance testing including stability and rate capability was evaluated. The temperature was found to impose a change on the valence and structure of the cathode materials. Specifically, manganese tends to be reduced at a high temperature of 800 °C and leads to structural changes. The manganese substituted LiMn 1.5Ni 0.5O 4more » (LMN) has proved to be a good candidate material for Li-ion battery cathodes displaying good rate capability and capacity retention. Finally, the cathode materials processed at 550 °C showed a stable performance with negligible capacity loss for 400 cycles.« less

Effect of overcharge on Li(Ni0.5Mn0.3Co0.2)O2/graphite lithium ion cells with poly(vinylidene fluoride) binder. III - Chemical changes in the cathode

NASA Astrophysics Data System (ADS)

Bareño, Javier; Dietz Rago, Nancy; Dogan, Fulya; Graczyk, Donald G.; Tsai, Yifen; Naik, Seema R.; Han, Sang-Don; Lee, Eungje; Du, Zhijia; Sheng, Yangping; Li, Jianlin; Wood, David L.; Steele, Leigh Anna; Lamb, Joshua; Spangler, Scott; Grosso, Christopher; Fenton, Kyle; Bloom, Ira

2018-05-01

1.5 Ah pouch cells based on Li(Ni0.5Mn0.3Co0.2)O2 cathodes and graphite anodes, both containing poly (vinylidene fluoride) (PVDF) binders, were systematically overcharged to 100, 120, 140, 160, 180, and 250% state of charge (SOC), at which point they vented. The cells were subsequently discharged to 0% SOC and disassembled under an inert atmosphere for characterization. A combination of X-ray photoelectron spectroscopy (XPS), scanning-electron microscopy (SEM), energy-dispersive spectroscopy (EDS), 6Li SSNMR, and X-ray diffraction (XRD) analysis of the NMC532 cathodes indicates the formation of a thin C- and O-rich cathode electrolyte interphase layer, progressive Li loss above 140% SOC, and retention of the bulk crystal structure at all states of charge.

Effect of overcharge on Li(Ni 0.5Mn 0.3Co 0.2)O 2/graphite lithium ion cells with poly(vinylidene fluoride) binder. III — Chemical changes in the cathode

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

Bareno, Javier; Dietz Rago, Nancy; Dogan, Fulya

Here, 1.5 Ah pouch cells based on Li(Ni 0.5Mn 0.3Co 0.2)O 2 cathodes and graphite anodes, both containing poly (vinylidene fluoride) (PVDF) binders, were systematically overcharged to 100, 120, 140, 160, 180, and 250% state of charge (SOC), at which point they vented. The cells were subsequently discharged to 0% SOC and disassembled under an inert atmosphere for characterization. A combination of X-ray photoelectron spectroscopy (XPS), scanning-electron microscopy (SEM), energy-dispersive spectroscopy (EDS), 6Li SSNMR, and X-ray diffraction (XRD) analysis of the NMC532 cathodes indicates the formation of a thin C- and O-rich cathode electrolyte interphase layer, progressive Li lossmore » above 140% SOC, and retention of the bulk crystal structure at all states of charge.« less

Tailored Core Shell Cathode Powders for Solid Oxide Fuel Cells

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

Swartz, Scott

2015-03-23

In this Phase I SBIR project, a “core-shell” composite cathode approach was evaluated for improving SOFC performance and reducing degradation of lanthanum strontium cobalt ferrite (LSCF) cathode materials, following previous successful demonstrations of infiltration approaches for achieving the same goals. The intent was to establish core-shell cathode powders that enabled high performance to be obtained with “drop-in” process capability for SOFC manufacturing (i.e., rather than adding an infiltration step to the SOFC manufacturing process). Milling, precipitation and hetero-coagulation methods were evaluated for making core-shell composite cathode powders comprised of coarse LSCF “core” particles and nanoscale “shell” particles of lanthanum strontiummore » manganite (LSM) or praseodymium strontium manganite (PSM). Precipitation and hetero-coagulation methods were successful for obtaining the targeted core-shell morphology, although perfect coverage of the LSCF core particles by the LSM and PSM particles was not obtained. Electrochemical characterization of core-shell cathode powders and conventional (baseline) cathode powders was performed via electrochemical impedance spectroscopy (EIS) half-cell measurements and single-cell SOFC testing. Reliable EIS testing methods were established, which enabled comparative area-specific resistance measurements to be obtained. A single-cell SOFC testing approach also was established that enabled cathode resistance to be separated from overall cell resistance, and for cathode degradation to be separated from overall cell degradation. The results of these EIS and SOFC tests conclusively determined that the core-shell cathode powders resulted in significant lowering of performance, compared to the baseline cathodes. Based on the results of this project, it was concluded that the core-shell cathode approach did not warrant further investigation.« less

Particle size-controllable microwave-assisted solvothermal synthesis of the high-voltage cathode material LiCoPO4 using water/ethylene glycol solvent blends

NASA Astrophysics Data System (ADS)

Ludwig, Jennifer; Haering, Dominik; Doeff, Marca M.; Nilges, Tom

2017-03-01

Particle size-tuned platelets of the high-voltage cathode material LiCoPO4 for Li-ion batteries have been synthesized by a simple one-step microwave-assisted solvothermal process using an array of water/ethylene glycol (EG) solvent mixtures. Particle size control was achieved by altering the concentration of the EG co-solvent in the mixture between 0 and 100 vol%, with amounts of 0-80 vol% EG producing single phase, olivine-type LiCoPO4. The particle sizes of the olivine materials were significantly reduced from about 1.2 μm × 1.2 μm × 500 nm (0 vol% EG) to 200 nm × 100 nm × 50 nm (80 vol% EG) with increasing EG content, while specific surface areas increased from 2 to 13 m2 g-1. The particle size reduction could mainly be attributed to the modified viscosities of the solvent blends. Owing to the soft template effect of EG, the crystals exhibited the smallest dimensions along the [010] direction of the Li diffusion pathways in the olivine crystal structure, resulting in enhanced lithium diffusion properties. The relationship between the synthesis, crystal properties and electrochemical performance was further elucidated, indicating that the electrochemical performances of the as-prepared materials mainly depend on the solvent composition and the respective particle size range. LiCoPO4 products obtained from reaction media with low and high EG contents exhibited good electrochemical performances (initial discharge capacities of 87-124 mAh g-1 at 0.1 C), whereas materials made from medium EG concentrations (40-60 vol% EG) showed the highest capacities and gravimetric energy densities (up to 137 mAh g-1 and 658 Wh kg-1 at 0.1 C), excellent rate capabilities, and cycle life.

An electrochemical study of a liquid crystal used in information displays

NASA Technical Reports Server (NTRS)

Oglesby, D. M.; Kern, J. B.; Robertson, J. B.

1974-01-01

The operational lifetime of liquid crystal displays were investigated. Electrochemical reaction at the electrodes of the display can cause failure after 2000 to 3000 hours of operation. Studies using cyclic voltametry of electrochemical reactions of N (p-methoxybenzilidene p-butylaniline (MBBA), a nematic liquid crystal were made. These studies indicate the presence of a reversible reduction of MBBA at the cathode, and that the reduction product undergoes a further reaction leading to products which are not reversibly oxidized. It is concluded that the degradation of the liquid crystal in displays can be reduced with a suitable frequency of alternating voltage.

Hydrothermal Synthesis of Nanostructured Manganese Oxide as Cathodic Catalyst in a Microbial Fuel Cell Fed with Leachate

PubMed Central

Haoran, Yuan; Lifang, Deng; Tao, Lu; Yong, Chen

2014-01-01

Much effort has been devoted to the synthesis of novel nanostructured MnO2 materials because of their unique properties and potential applications as cathode catalyst in Microbial fuel cell. Hybrid MnO2 nanostructures were fabricated by a simple hydrothermal method in this study. Their crystal structures, morphology, and electrochemical characters were carried out by FESEM, N2-adsorption-desorption, and CV, indicating that the hydrothermally synthesized MnO2 (HSM) was structured by nanorods of high aspect ratio and multivalve nanoflowers and more positive than the naturally synthesized MnO2 (NSM), accompanied by a noticeable increase in oxygen reduction peak current. When the HSM was employed as the cathode catalyst in air-cathode MFC which fed with leachate, a maximum power density of 119.07 mW/m2 was delivered, 64.68% higher than that with the NSM as cathode catalyst. Furthermore, the HSM via a 4-e pathway, but the NSM via a 2-e pathway in alkaline solution, and as 4-e pathway is a more efficient oxygen reduction reaction, the HSM was more positive than NSM. Our study provides useful information on facile preparation of cost-effective cathodic catalyst in air-cathode MFC for wastewater treatment. PMID:24723824

The 15 cm diameter ion thruster research

NASA Technical Reports Server (NTRS)

Wilbur, P. J.

1974-01-01

The startup reliability of a 15 cm diameter mercury bombardment ion thruster which employs a pulsed high voltage tickler electrode on the main and neutralizer cathodes is examined. Startup of the thruster is achieved 100% of the time on the main cathode and 98.7% of the time on the neutralizer cathode over a 3640 cycle test. The thruster was started from a 20 C initial condition and operated for an hour at a 600 mA beam current. An energy efficiency of 75% and a propellant utilization efficiency of 77% was achieved over the complete cycle. The effect of a single cusp magnetic field thruster length on its performance is discussed. Guidelines are formulated for the shaping of magnetic field lines in thrusters. A model describing double ion production in mercury discharges is presented. The production route is shown to occur through the single ionic ground state. Photographs of the interior of an operating-hollow cathode are presented. A cathode spot is shown to be present if the cathode is free of low work-function surfaces. The spot is observed if a low work-function oxide coating is applied to the cathode insert. Results show that low work-function oxide coatings tend to migrate during thruster operation.

A new hexanuclear iron-selenium nitrosyl cluster: primary exploration of the preparation methods, structure, and spectroscopic and electrochemical properties.

PubMed

Wang, Rongming; Xu, Wei; Zhang, Jian; Li, Lijuan

2010-06-07

A new hexanuclear iron-selenium nitrosyl cluster, [(n-Bu)(4)N](2)[Fe(6)Se(6)(NO)(6)] (1), and a hexanuclear iron-sulfur nitrosyl cluster, [(n-Bu)(4)N](2)[Fe(6)S(6)(NO)(6)] (2), were synthesized by the solvent-thermal reactions of [(n-Bu)(4)N][Fe(CO)(3)NO] with selenium or sulfur in methanol, while a tetranuclear iron-sulfur nitrosyl cluster, (Me(4)N)[Fe(4)S(3)(NO)(7)] (3), was also prepared by the solvent-thermal reaction of FeCl(2).4H(2)O with thiourea in the presence of (CH(3))(4)NCl, NaNO(2), and methanol. Complexes 1-3 were characterized by IR, UV-vis, (1)H NMR, electrochemistry, and single-crystal X-ray diffraction analysis. IR spectra of complexes 1 and 2 show the characteristic NO stretching frequencies at 1694 and 1698 cm(-1), respectively, while the absorptions of complex 3 appear at 1799, 1744, and 1710 cm(-1). The UV-vis spectra of complexes 1-3 show different bands in the range of 259-562 nm, which are assigned to the transitions between orbitals delocalized over the Fe-S cluster, the ligand-to-metal charge transfer, pi*(NO)-d(Fe), and the metal-to-ligand charge transfer, d(Fe)-pi*(NO). Single-crystal X-ray structural analysis reveals that complex 1 crystallizes in the monoclinic P2(1)/n space group with two molecules per unit cell. Two parallel "chair-shaped" structures, consisting of three iron and three selenium atoms, are connected by Fe-Se bonds with an average distance of 2.341 A; each iron center is bonded to three selenium atoms and a nitrogen atom from the nitrosyl ligand with a pseudotetrahedral center geometry. Cyclic voltammograms of complexes 1 and 2 display two cathodic and three anodic current peaks with an unusually strong cathodic peak. Further electrochemical investigations demonstrated that the intensity of the unusually strong peak is a result of at least three processes. One is the quasi-reversible reduction, and the other two are from an irreversible electrochemical process, in which the compound goes through a typical electron transfer and chemical reaction mechanism. Compound 3 shows three quasi-reversible reductions.

Raman microscopy of lithium-manganese-rich transition metal oxide cathodes

DOE PAGES

Ruther, Rose E.; Callender, Andrew F.; Zhou, Hui; ...

2014-11-15

Lithium-rich and manganese-rich (LMR) layered transition metal (TM) oxide composites with general formula xLi 2MnO 3·(1-x)LiMO 2 (M = Ni, Co, Mn) are promising cathode candidates for high energy density lithium ion batteries. Lithium-manganese-rich TM oxides crystallize as a nanocomposite layered phase whose structure further evolves with electrochemical cycling. Raman spectroscopy is a powerful tool to monitor the crystal chemistry and correlate phase changes with electrochemical behavior. While several groups have reported Raman spectra of lithium rich TM oxides, the data show considerable variability in terms of both the vibrational features observed and their interpretation. In this paper, Raman microscopymore » is used to investigate lithium-rich and manganese-rich TM cathodes as a function of voltage and electrochemical cycling at various temperatures. No growth of a spinel phase is observed within the cycling conditions. However, analysis of the Raman spectra does indicate the structure of LMR-NMC deviates significantly from an ideal layered phase. Finally, the results also highlight the importance of using low laser power and large sample sizes to obtain consistent data sets.« less

Correlation of intercalation potential with d-electron configurations for cathode compounds of lithium-ion batteries.

PubMed

Chen, Zhenlian; Zhang, Caixia; Zhang, Zhiyong; Li, Jun

2014-07-14

The d-electron localization is widely recognized as important to transport properties of transition metal compounds, but its role in the energy conversion of intercalation reactions of cathode compounds is still not fully explored. In this work, the correlation of intercalation potential with electron affinity, a key energy term controlling electron intercalation, then with d-electron configuration, is investigated. Firstly, we find that the change of the intercalation potential with respect to the transition metal cations within the same structure class is correlated in an approximately mirror relationship with the electron affinity, based on first-principles calculations on three typical categories of cathode compounds including layered oxides and polyoxyanions Then, by using a new model Hamiltonian based on the crystal-field theory, we reveal that the evolution is governed by the combination of the crystal-field splitting and the on-site d-d exchange interactions. Further, we show that the charge order in solid-solution composites and the compatibility of multi-electron redox steps could be inferred from the energy terms with the d-electron configuration alternations. These findings may be applied to rationally designing new chemistry for the lithium-ion batteries and other metal-ion batteries.

Suppressing Manganese Dissolution from Lithium Manganese Oxide Spinel Cathodes with Single-Layer Graphene

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

Jaber-Ansari, Laila; Puntambekar, Kanan P.; Kim, Soo

2015-06-24

Spinel-structured LiMn 2 O 4 (LMO) is a desirable cathode material for Li-ion batteries due to its low cost, abundance, and high power capability. However, LMO suffers from limited cycle life that is triggered by manganese dissolution into the electrolyte during electrochemical cycling. Here, it is shown that single-layer graphene coatings suppress manganese dissolution, thus enhancing the performance and lifetime of LMO cathodes. Relative to lithium cells with uncoated LMO cathodes, cells with graphene-coated LMO cathodes provide improved capacity retention with enhanced cycling stability. X-ray photoelectron spectroscopy reveals that graphene coatings inhibit manganese depletion from the LMO surface. Additionally, transmissionmore » electron microscopy demonstrates that a stable solid electrolyte interphase is formed on graphene, which screens the LMO from direct contact with the electrolyte. Density functional theory calculations provide two mechanisms for the role of graphene in the suppression of manganese dissolution. First, common defects in single-layer graphene are found to allow the transport of lithium while concurrently acting as barriers for manganese diffusion. Second, graphene can chemically interact with Mn 3+ at the LMO electrode surface, promoting an oxidation state change to Mn 4+ , which suppresses dissolution.« less

High performance platinum single atom electrocatalyst for oxygen reduction reaction

NASA Astrophysics Data System (ADS)

Liu, Jing; Jiao, Menggai; Lu, Lanlu; Barkholtz, Heather M.; Li, Yuping; Wang, Ying; Jiang, Luhua; Wu, Zhijian; Liu, Di-Jia; Zhuang, Lin; Ma, Chao; Zeng, Jie; Zhang, Bingsen; Su, Dangsheng; Song, Ping; Xing, Wei; Xu, Weilin; Wang, Ying; Jiang, Zheng; Sun, Gongquan

2017-07-01

For the large-scale sustainable implementation of polymer electrolyte membrane fuel cells in vehicles, high-performance electrocatalysts with low platinum consumption are desirable for use as cathode material during the oxygen reduction reaction in fuel cells. Here we report a carbon black-supported cost-effective, efficient and durable platinum single-atom electrocatalyst with carbon monoxide/methanol tolerance for the cathodic oxygen reduction reaction. The acidic single-cell with such a catalyst as cathode delivers high performance, with power density up to 680 mW cm-2 at 80 °C with a low platinum loading of 0.09 mgPt cm-2, corresponding to a platinum utilization of 0.13 gPt kW-1 in the fuel cell. Good fuel cell durability is also observed. Theoretical calculations reveal that the main effective sites on such platinum single-atom electrocatalysts are single-pyridinic-nitrogen-atom-anchored single-platinum-atom centres, which are tolerant to carbon monoxide/methanol, but highly active for the oxygen reduction reaction.

High performance platinum single atom electrocatalyst for oxygen reduction reaction

PubMed Central

Liu, Jing; Jiao, Menggai; Lu, Lanlu; Barkholtz, Heather M.; Li, Yuping; Wang, Ying; Jiang, Luhua; Wu, Zhijian; Liu, Di-jia; Zhuang, Lin; Ma, Chao; Zeng, Jie; Zhang, Bingsen; Su, Dangsheng; Song, Ping; Xing, Wei; Xu, Weilin; Wang, Ying; Jiang, Zheng; Sun, Gongquan

2017-01-01

For the large-scale sustainable implementation of polymer electrolyte membrane fuel cells in vehicles, high-performance electrocatalysts with low platinum consumption are desirable for use as cathode material during the oxygen reduction reaction in fuel cells. Here we report a carbon black-supported cost-effective, efficient and durable platinum single-atom electrocatalyst with carbon monoxide/methanol tolerance for the cathodic oxygen reduction reaction. The acidic single-cell with such a catalyst as cathode delivers high performance, with power density up to 680 mW cm−2 at 80 °C with a low platinum loading of 0.09 mgPt cm−2, corresponding to a platinum utilization of 0.13 gPt kW−1 in the fuel cell. Good fuel cell durability is also observed. Theoretical calculations reveal that the main effective sites on such platinum single-atom electrocatalysts are single-pyridinic-nitrogen-atom-anchored single-platinum-atom centres, which are tolerant to carbon monoxide/methanol, but highly active for the oxygen reduction reaction. PMID:28737170

Electrosynthesis of cerium hexaboride by the molten salt technique

NASA Astrophysics Data System (ADS)

Amalajyothi, K.; Berchmans, L. John; Angappan, S.; Visuvasam, A.

2008-07-01

Molten salts are well thought-out as the incredibly promising medium for chemical and electrochemical synthesis of compounds. Hence a stab has been made on the electrochemical synthesis of CeB 6 using molten salt technique. The electrolyte consisted of lithium fluoride (LiF), boron trioxide (B 2O 3) and cerium chloride (CeCl 3). Electrochemical experiments were carried out in an inconal reactor in an argon atmosphere. Electrolysis was executed in a high-density graphite crucible, which doles out as the electrolyte clutching vessel as well as the anode. The cathode was made up of a molybdenum rod. The electrolysis was carried out at 900 °C at different current densities intended for the synthesis of CeB 6 crystals. After the electrolysis, the cathode product was removed and cleaned using dilute HCl solution. The crystals were scrutinized by X-ray diffraction (XRD) to make out the phase and the purity. It has been observed that CeB 6 crystals are synthesized at all current densities and the product has traces of impurities.

A highly active hybrid catalyst modified (La 0.60Sr 0.40) 0.95Co 0.20Fe 0.80O 3-δ cathode for proton conducting solid oxide fuel cells

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

Lei, Libin; Tao, Zetian; Hong, Tao

The sluggish reaction kinetics in the cathode usually leads to considerable cathode polarization resistance, hindering the development of proton conducting solid oxide fuel cells (H-SOFCs) operated at intermediate temperatures (400–650 °C). In this paper, to address this problem, for the first time, a novel hybrid catalyst consisting of PrNi 0.5Mn 0.5O 3 and PrOx is impregnated in the (La 0.60Sr 0.40) 0.95Co 0.20Fe 0.80O 3-δ (LSCF) cathode of H-SOFCs, resulting in significant enhancement of the cathode reaction kinetics. Single cells with impregnated LSCF cathode and BaZr 0.8Y 0.2O 3 (BZY) electrolyte yield a maximum power density (MPD) of 0.198 Wmore » cm -2 at 600 °C, more than doubled of that with blank LSCF cathode (0.083 W cm -2). ECR and EIS studies reveal that the hybrid catalyst can substantially accelerate the oxygen-ion transfer and oxygen dissociation-absorption processes in the cathode, resulting in significantly lower polarization resistance and higher MPD. In addition, the hybrid catalyst possesses good chemical and microstructural stability at 600 °C. Consequently, the single cells with impregnated LSCF cathode show excellent durability. Finally, this study shows that the impregnation of this novel hybrid catalyst in the cathode could be a promising approach to improve the performance and stability of H-SOFCs.« less

A highly active hybrid catalyst modified (La 0.60Sr 0.40) 0.95Co 0.20Fe 0.80O 3-δ cathode for proton conducting solid oxide fuel cells

DOE PAGES

Lei, Libin; Tao, Zetian; Hong, Tao; ...

2018-04-06

The sluggish reaction kinetics in the cathode usually leads to considerable cathode polarization resistance, hindering the development of proton conducting solid oxide fuel cells (H-SOFCs) operated at intermediate temperatures (400–650 °C). In this paper, to address this problem, for the first time, a novel hybrid catalyst consisting of PrNi 0.5Mn 0.5O 3 and PrOx is impregnated in the (La 0.60Sr 0.40) 0.95Co 0.20Fe 0.80O 3-δ (LSCF) cathode of H-SOFCs, resulting in significant enhancement of the cathode reaction kinetics. Single cells with impregnated LSCF cathode and BaZr 0.8Y 0.2O 3 (BZY) electrolyte yield a maximum power density (MPD) of 0.198 Wmore » cm -2 at 600 °C, more than doubled of that with blank LSCF cathode (0.083 W cm -2). ECR and EIS studies reveal that the hybrid catalyst can substantially accelerate the oxygen-ion transfer and oxygen dissociation-absorption processes in the cathode, resulting in significantly lower polarization resistance and higher MPD. In addition, the hybrid catalyst possesses good chemical and microstructural stability at 600 °C. Consequently, the single cells with impregnated LSCF cathode show excellent durability. Finally, this study shows that the impregnation of this novel hybrid catalyst in the cathode could be a promising approach to improve the performance and stability of H-SOFCs.« less

4D multiple-cathode ultrafast electron microscopy

PubMed Central

Baskin, John Spencer; Liu, Haihua; Zewail, Ahmed H.

2014-01-01

Four-dimensional multiple-cathode ultrafast electron microscopy is developed to enable the capture of multiple images at ultrashort time intervals for a single microscopic dynamic process. The dynamic process is initiated in the specimen by one femtosecond light pulse and probed by multiple packets of electrons generated by one UV laser pulse impinging on multiple, spatially distinct, cathode surfaces. Each packet is distinctly recorded, with timing and detector location controlled by the cathode configuration. In the first demonstration, two packets of electrons on each image frame (of the CCD) probe different times, separated by 19 picoseconds, in the evolution of the diffraction of a gold film following femtosecond heating. Future elaborations of this concept to extend its capabilities and expand the range of applications of 4D ultrafast electron microscopy are discussed. The proof-of-principle demonstration reported here provides a path toward the imaging of irreversible ultrafast phenomena of materials, and opens the door to studies involving the single-frame capture of ultrafast dynamics using single-pump/multiple-probe, embedded stroboscopic imaging. PMID:25006261

4D multiple-cathode ultrafast electron microscopy.

PubMed

Baskin, John Spencer; Liu, Haihua; Zewail, Ahmed H

2014-07-22

Four-dimensional multiple-cathode ultrafast electron microscopy is developed to enable the capture of multiple images at ultrashort time intervals for a single microscopic dynamic process. The dynamic process is initiated in the specimen by one femtosecond light pulse and probed by multiple packets of electrons generated by one UV laser pulse impinging on multiple, spatially distinct, cathode surfaces. Each packet is distinctly recorded, with timing and detector location controlled by the cathode configuration. In the first demonstration, two packets of electrons on each image frame (of the CCD) probe different times, separated by 19 picoseconds, in the evolution of the diffraction of a gold film following femtosecond heating. Future elaborations of this concept to extend its capabilities and expand the range of applications of 4D ultrafast electron microscopy are discussed. The proof-of-principle demonstration reported here provides a path toward the imaging of irreversible ultrafast phenomena of materials, and opens the door to studies involving the single-frame capture of ultrafast dynamics using single-pump/multiple-probe, embedded stroboscopic imaging.

Synthesis and structural stability of Cr-doped Li2MnSiO4/C cathode materials by solid-state method

NASA Astrophysics Data System (ADS)

Cheng, Hong-Mei; Zhao, Shi-Xi; Wu, Xia; Zhao, Jian-Wei; Wei, Lei; Nan, Ce-Wen

2018-03-01

The crystal structure of the Li2MnSiO4 cathode material would collapse during the charge and discharge process because of that the Mn-O coordination polyhedron changed from [MnO4] into [MnO6] in the process of Mn+2 to Mn+4, but the Cr element could remain [CrO4] crystal ligand from Cr+2 to Cr+4, so Cr element substitution was used to improve the structural stability of the Li2MnSiO4 cathode material. In this work, Li2Mn1-xCrxSiO4/C nanocomposites were synthesized by solid-state method. XRD, SEM and TEM observations show that the as-prepared Li2Mn1-xCrxSiO4/C materials presents an orthorhombic crystal structure (S.G. Pmn21), the particle size of Li2Mn1-xCrxSiO4/C powder ranges from 50 to 100 nm. The XRD and XPS results indicate that Cr+2 is successfully doped into Li2MnSiO4 lattice and has well compatibility with Li2MnSiO4. The electrochemical results display that Li2Mn92.5%Cr7.5%SiO4/C exhibits significantly enhanced cycle stability and discharge capability. The initial discharge capacity of the Li2Mn92.5%Cr7.5%SiO4/C sample is 255 mAh g-1, and the discharge capacity was still about 60 mAh g-1 after 50 cycles. Furthermore, the XRD patterns, TEM images and Raman analysis reveal that the Cr doping enhances the structural stability of Li2Mn1-xCrxSiO4/C and improves the electrochemical activity of the cathode. Thus, the Li2Mn92.5%Cr7.5%SiO4/C have shown potential applications for lithium ion batteries.

Transparent ITO/Ag-Pd-Cu/ITO multilayer cathode use in inverted organic solar cells

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

Kim, Hyo-Joong; Kim, Han-Ki, E-mail: imdlhkkim@khu.ac.kr; Lee, Hyun Hwi

2015-10-15

The characteristics of transparent ITO/Ag-Pd-Cu (APC)/ITO multilayer cathodes were investigated for use in inverted organic solar cells (IOSCs). The insertion of an APC interlayer into the ITO film effectively led to crystallization of the top ITO layer, unlike that in the Ag interlayer, and resulted in a low sheet resistance of 6.55 Ohm/square and a high optical transmittance of 84.14% without post annealing. In addition, the alloying of the Pd and Cu elements into Ag prevented agglomeration and oxidization of the metal interlayer and led to more stable ITO/APC/ITO films under ambient conditions. The microstructure and interfacial structure of themore » transparent ITO/APC/ITO cathode in the IOSCs were examined in detail by synchrotron X-ray scattering and high resolution transmission electron microscopy. Furthermore, we suggested a possible mechanism to explain the lower PCE of the IOSCs with an ITO/APC/ITO cathode than that of a reference IOSC with a crystalline ITO cathode using the external quantum efficiency of the IOSCs.« less

The performance of spinel bulk-like oxygen-deficient CoGa2O4 as an air-cathode catalyst in microbial fuel cell

NASA Astrophysics Data System (ADS)

Liu, Di; Mo, Xiaoping; Li, Kexun; Liu, Yi; Wang, Junjie; Yang, Tingting

2017-08-01

Nano spinel bulk-like CoGa2O4 prepared via a facile hydrothermal method is used as a high efficient electrochemical catalyst in activated carbon (AC) air-cathode microbial fuel cell (MFC). The maximum power density of the modified MFC is 1911 ± 49 mW m-2, 147% higher than the MFC of untreated AC cathode. Transmission electron microscope (TEM) and X-ray diffraction (XRD) exhibit the morphology and crystal structure of CoGa2O4. Rotating disk electrode (RDE) confirms the four-electron pathway at the cathode during the oxygen reduction reaction (ORR). Thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS) illustrate that the high rate oxygen vacancy exist in the CoGa2O4. The oxygen vacancy of CoGa2O4 plays an important role in catalytic activity. In a word, the prepared nano spinel bulk-like CoGa2O4 provides an alternative to the costly Pt in air-cathode for power output.

Self-Substitution and the Temperature Effects on the Electrochemical Performance in the High Voltage Cathode System LiMn 1.5+xNi 0.5-xO 4 (x = 0.1)

DOE PAGES

Xu, Yun; Zhao, Mingyang; Khalid, Syed; ...

2017-05-09

The high voltage cathode material, LiMn 1.6Ni 0.4O 4, was prepared by a polymer-assisted method. The novelty of this paper is the substitution of Ni with Mn, which already exists in the crystal structure instead of other isovalent metal ion dopants which would result in capacity loss. The electrochemical performance testing including stability and rate capability was evaluated. The temperature was found to impose a change on the valence and structure of the cathode materials. Specifically, manganese tends to be reduced at a high temperature of 800 °C and leads to structural changes. The manganese substituted LiMn 1.5Ni 0.5O 4more » (LMN) has proved to be a good candidate material for Li-ion battery cathodes displaying good rate capability and capacity retention. Finally, the cathode materials processed at 550 °C showed a stable performance with negligible capacity loss for 400 cycles.« less

Perspectives on Li and transition metal fluoride phosphates as cathode materials for a new generation of Li-ion batteries.

PubMed

Antipov, Evgeny V; Khasanova, Nellie R; Fedotov, Stanislav S

2015-01-01

To satisfy the needs of rapidly growing applications, Li-ion batteries require further significant improvements of their key properties: specific energy and power, cyclability, safety and costs. The first generation of cathode materials for Li-ion batteries based on mixed oxides with either spinel or rock-salt derivatives has already been widely commercialized, but the potential to improve the performance of these materials further is almost exhausted. Li and transition metal inorganic compounds containing different polyanions are now considered as the most promising cathode materials for the next generation of Li-ion batteries. Further advances in cathode materials are considered to lie in combining different anions [such as (XO4) (n-) and F(-)] in the anion sublattice, which is expected to enhance the specific energy and power of these materials. This review focuses on recent advances related to the new class of cathode materials for Li-ion batteries containing phosphate and fluoride anions. Special attention is given to their crystal structures and the relationships between structure and properties, which are important for their possible practical applications.

Transparent ITO/Ag-Pd-Cu/ITO multilayer cathode use in inverted organic solar cells

NASA Astrophysics Data System (ADS)

Kim, Hyo-Joong; Lee, Hyun Hwi; Kal, Jinha; Hahn, Jungseok; Kim, Han-Ki

2015-10-01

The characteristics of transparent ITO/Ag-Pd-Cu (APC)/ITO multilayer cathodes were investigated for use in inverted organic solar cells (IOSCs). The insertion of an APC interlayer into the ITO film effectively led to crystallization of the top ITO layer, unlike that in the Ag interlayer, and resulted in a low sheet resistance of 6.55 Ohm/square and a high optical transmittance of 84.14% without post annealing. In addition, the alloying of the Pd and Cu elements into Ag prevented agglomeration and oxidization of the metal interlayer and led to more stable ITO/APC/ITO films under ambient conditions. The microstructure and interfacial structure of the transparent ITO/APC/ITO cathode in the IOSCs were examined in detail by synchrotron X-ray scattering and high resolution transmission electron microscopy. Furthermore, we suggested a possible mechanism to explain the lower PCE of the IOSCs with an ITO/APC/ITO cathode than that of a reference IOSC with a crystalline ITO cathode using the external quantum efficiency of the IOSCs.

Electrochemical power-producing cell. [Li/Se

DOEpatents

Cairns, E.J.; Chilenskas, A.A.; Steunenberg, R.K.; Shimotake, H.

1972-05-30

An electrochemical power-producing cell including a molten lithium metal anode, a molten selenium metal cathode, a paste electrolyte separating the anode from the cathode, an anode current collector, and a single layer of niobium expanded metal formed in corrugated shape as cathode current collector is described. In addition, means are provided for sealing the anode and the cathode from loss of lithium and selenium, respectively, and an insulator is provided between the anode housing and the paste electrolyte disk.

Inhibition of microbial growth on air cathodes of single chamber microbial fuel cells by incorporating enrofloxacin into the catalyst layer.

PubMed

Liu, Weifeng; Cheng, Shaoan; Sun, Dan; Huang, Haobin; Chen, Jie; Cen, Kefa

2015-10-15

The inevitable growth of aerobic bacteria on the surface of air cathodes is an important factor reducing the performance stability of air cathode single-chamber membrane-free microbial fuel cells (MFCs). Thus searching for effective methods to inhibit the cathodic microbial growth is critical for the practical application of MFCs. In this study, enrofloxacin (ENR), a broad spectrum fluoroquinolone antibiotic, was incorporated into the catalyst layer of activated carbon air cathodes (ACACs) to inhibit the cathodic microbial growth. The biomass content on ACACs was substantially reduced by 60.2% with ENR treatment after 91 days of MFCs operation. As a result of the inhibited microbial growth, the oxygen reduction catalytic performance of the ENR treated ACACs was much stable compared to the fast performance decline of the untreated control. Consequently, a quite stable electricity production was obtained for the MFCs with the ENR treated ACACs, in contrast with a 22.5% decrease in maximum power density of the MFCs with the untreated cathode. ENR treatment of ACACs showed minimal effects on the anode performance. These results indicate that incorporating antibiotics into ACACs should be a simple and effective strategy to inhibit the microbial growth and improve the long-term stability of the performance of air cathode and the electricity production of MFCs. Copyright © 2015 Elsevier B.V. All rights reserved.

Management practices for end-of-life cathode ray tube glass: Review of advances in recycling and best available technologies.

PubMed

Iniaghe, Paschal O; Adie, Gilbert U

2015-11-01

Cathode ray tubes are image display units found in computer monitors and televisions. In recent years, cathode ray tubes have been generated as waste owing to the introduction of newer and advanced technologies in image displays, such as liquid crystal displays and high definition televisions, among others. Generation and subsequent disposal of end-of-life cathode ray tubes presents a challenge owing to increasing volumes and high lead content embedded in the funnel and neck sections of the glass. Disposal in landfills and open dumping are anti-environmental practices considering the large-scale contamination of environmental media by the potential of toxic metals leaching from glass. Mitigating such environmental contamination will require sound management strategies that are environmentally friendly and economically feasible. This review covers existing and emerging management practices for end-of-life cathode ray tubes. An in-depth analysis of available technologies (glass smelting, detoxification of cathode ray tube glass, lead extraction from cathode ray tube glass) revealed that most of the techniques are environmentally friendly, but are largely confined to either laboratory scale, or are often limited owing to high cost to mount, or generate secondary pollutants, while a closed-looped method is antiquated. However, recycling in cementitious systems (cement mortar and concrete) gives an added advantage in terms of quantity of recyclable cathode ray tube glass at a given time, with minimal environmental and economic implications. With significant quantity of waste cathode ray tube glass being generated globally, cementitious systems could be economically and environmentally acceptable as a sound management practice for cathode ray tube glass, where other technologies may not be applicable. © The Author(s) 2015.

Full open-framework batteries for stationary energy storage

NASA Astrophysics Data System (ADS)

Pasta, Mauro; Wessells, Colin D.; Liu, Nian; Nelson, Johanna; McDowell, Matthew T.; Huggins, Robert A.; Toney, Michael F.; Cui, Yi

2014-01-01

New types of energy storage are needed in conjunction with the deployment of renewable energy sources and their integration with the electrical grid. We have recently introduced a family of cathodes involving the reversible insertion of cations into materials with the Prussian Blue open-framework crystal structure. Here we report a newly developed manganese hexacyanomanganate open-framework anode that has the same crystal structure. By combining it with the previously reported copper hexacyanoferrate cathode we demonstrate a safe, fast, inexpensive, long-cycle life aqueous electrolyte battery, which involves the insertion of sodium ions. This high rate, high efficiency cell shows a 96.7% round trip energy efficiency when cycled at a 5C rate and an 84.2% energy efficiency at a 50C rate. There is no measurable capacity loss after 1,000 deep-discharge cycles. Bulk quantities of the electrode materials can be produced by a room temperature chemical synthesis from earth-abundant precursors.

Full open-framework batteries for stationary energy storage.

PubMed

Pasta, Mauro; Wessells, Colin D; Liu, Nian; Nelson, Johanna; McDowell, Matthew T; Huggins, Robert A; Toney, Michael F; Cui, Yi

2014-01-01

New types of energy storage are needed in conjunction with the deployment of renewable energy sources and their integration with the electrical grid. We have recently introduced a family of cathodes involving the reversible insertion of cations into materials with the Prussian Blue open-framework crystal structure. Here we report a newly developed manganese hexacyanomanganate open-framework anode that has the same crystal structure. By combining it with the previously reported copper hexacyanoferrate cathode we demonstrate a safe, fast, inexpensive, long-cycle life aqueous electrolyte battery, which involves the insertion of sodium ions. This high rate, high efficiency cell shows a 96.7% round trip energy efficiency when cycled at a 5C rate and an 84.2% energy efficiency at a 50C rate. There is no measurable capacity loss after 1,000 deep-discharge cycles. Bulk quantities of the electrode materials can be produced by a room temperature chemical synthesis from earth-abundant precursors.

A mixed iron-manganese based pyrophosphate cathode, Na2Fe0.5Mn0.5P2O7, for rechargeable sodium ion batteries.

PubMed

Shakoor, Rana A; Park, Chan Sun; Raja, Arsalan A; Shin, Jaeho; Kahraman, Ramazan

2016-02-07

The development of secondary batteries based on abundant and cheap elements is vital. Among various alternatives to conventional lithium-ion batteries, sodium-ion batteries (SIBs) are promising due to the abundant resources and low cost of sodium. While there are many challenges associated with the SIB system, cathode is an important factor in determining the electrochemical performance of this battery system. Accordingly, ongoing research in the field of SIBs is inclined towards the development of safe, cost effective cathode materials having improved performance. In particular, pyrophosphate cathodes have recently demonstrated decent electrochemical performance and thermal stability. Herein, we report the synthesis, electrochemical properties, and thermal behavior of a novel Na2Fe0.5Mn0.5P2O7 cathode for SIBs. The material was synthesized through a solid state process. The structural analysis reveals that the mixed substitution of manganese and iron has resulted in a triclinic crystal structure (P1[combining macron] space group). Galvanostatic charge/discharge measurements indicate that Na2Fe0.5Mn0.5P2O7 is electrochemically active with a reversible capacity of ∼80 mA h g(-1) at a C/20 rate with an average redox potential of 3.2 V. (vs. Na/Na(+)). It is noticed that 84% of initial capacity is preserved over 90 cycles showing promising cyclability. It is also noticed that the rate capability of Na2Fe0.5Mn0.5P2O7 is better than Na2MnP2O7. Ex situ and CV analyses indicate that Na2Fe0.5Mn0.5P2O7 undergoes a single phase reaction rather than a biphasic reaction due to different Na coordination environment and different Na site occupancy when compared to other pyrophosphate materials (Na2FeP2O7 and Na2MnP2O7). Thermogravimetric analysis (25-550 °C) confirms good thermal stability of Na2Fe0.5Mn0.5P2O7 with only 2% weight loss. Owing to promising electrochemical properties and decent thermal stability, Na2Fe0.5Mn0.5P2O7, can be an attractive cathode for SIBs.

Investigation of structural and electrochemical properties of LaSrCo{sub 1−x}Sb{sub x}O{sub 4} (0≤x≤0.20) as potential cathode materials in intermediate-temperature solid oxide fuel cells

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

Wang, Junkai; Zhou, Jun, E-mail: zhoujun@mail.xjtu.edu.cn; Fan, Weiwei

The structural and electrochemical properties of the layered perovskite oxides LaSrCo{sub 1−x}Sb{sub x}O{sub 4} (0≤x≤0.20) were investigated to study the effects of substituting Sb for Co for application as cathode materials in intermediate temperature solid oxide fuel cells (IT-SOFCs). The results of crystal structure analyses show the maximum content of Sb in LaSrCo{sub 1−x}Sb{sub x}O{sub 4} to be 0.05 as a pure single phase. XPS shows that Co and Sb in LaSrCo{sub 0.95}Sb{sub 0.05}O{sub 4} may possess mixed-oxidation states. The electrical conductivity increased greatly after Sb substitution. An improvement in the cathode polarization (R{sub p}) values is observed from themore » Sb-doped sample with respect to the undoped samples. For example, R{sub p} of LaSrCo{sub 0.95}Sb{sub 0.05}O{sub 4} on LSGM was observed to be 0.16 Ω cm{sup 2} at 800 °C in air. The main rate-limiting step for LaSrCo{sub 0.95}Sb{sub 0.05}O{sub 4} cathode is charge transfer of oxygen atoms. These results indicate that Sb can be incorporated into LaSrCo{sub 1−x}Sb{sub x}O{sub 4} based materials and can have a beneficial effect on the performance, making them potentially suitable for use as cathode materials in IT-SOFCs. - Graphical abstract: The oxygen partial pressure dependence of polarization resistances for a new layered perovskite cathode LaSrCo{sub 0.95}Sb{sub 0.05}O{sub 4} at various temperatures was measured. - Highlights: • The maximum content of Sb was 0.05 mol in LaSrCo{sub 1−x}Sb{sub x}O{sub 4}. • The maximum electrical conductivity is 194 S cm{sup −1}for LaSrCo{sub 0.95}Sb{sub 0.05}O{sub 4} at 800 °C. • A rate-limiting process of charge transfer presented.« less

Formation of nanocrystalline tetragonal oxide tungsten bronzes on platinum

NASA Astrophysics Data System (ADS)

Kosov, A. V.; Semerikova, O. L.; Vakarin, S. V.; Pankratov, A. A.; Plaksin, S. V.; Zaykov, Yu. P.

2017-02-01

Cyclic voltammetry is used to study the formation of tetragonal oxide tungsten bronze of the composition K x Na y WO3 on a Pt(110) substrate during electrodeposition from a K2WO4-Na2WO4-WO3 melt. The potential ranges in which cathode products of various compositions and morphologies form are found. K x Na(0.66- x)WO3 crystals are shown to form according to the nucleation/growth mechanism. A general scheme is proposed and used to write equations for cathode reactions.

Cu-Ni-Fe anodes having improved microstructure

DOEpatents

Bergsma, S. Craig; Brown, Craig W.

2004-04-20

A method of producing aluminum in a low temperature electrolytic cell containing alumina dissolved in an electrolyte. The method comprises the steps of providing a molten electrolyte having alumina dissolved therein in an electrolytic cell containing the electrolyte. A non-consumable anode and cathode is disposed in the electrolyte, the anode comprised of Cu--Ni--Fe alloys having single metallurgical phase. Electric current is passed from the anode, through the electrolyte to the cathode thereby depositing aluminum on the cathode, and molten aluminum is collected from the cathode.

Fast Atomic-Scale Chemical Imaging of Crystalline Materials and Dynamic Phase Transformations.

PubMed

Lu, Ping; Yuan, Ren Liang; Ihlefeld, Jon F; Spoerke, Erik David; Pan, Wei; Zuo, Jian Min

2016-04-13

Atomic-scale phenomena fundamentally influence materials form and function that makes the ability to locally probe and study these processes critical to advancing our understanding and development of materials. Atomic-scale chemical imaging by scanning transmission electron microscopy (STEM) using energy-dispersive X-ray spectroscopy (EDS) is a powerful approach to investigate solid crystal structures. Inefficient X-ray emission and collection, however, require long acquisition times (typically hundreds of seconds), making the technique incompatible with electron-beam sensitive materials and study of dynamic material phenomena. Here we describe an atomic-scale STEM-EDS chemical imaging technique that decreases the acquisition time to as little as one second, a reduction of more than 100 times. We demonstrate this new approach using LaAlO3 single crystal and study dynamic phase transformation in beam-sensitive Li[Li0.2Ni0.2Mn0.6]O2 (LNMO) lithium ion battery cathode material. By capturing a series of time-lapsed chemical maps, we show for the first time clear atomic-scale evidence of preferred Ni-mobility in LNMO transformation, revealing new kinetic mechanisms. These examples highlight the potential of this approach toward temporal, atomic-scale mapping of crystal structure and chemistry for investigating dynamic material phenomena.

Permittivity changes induced by injected electrons and field-induced phase transition in KTa1-xNbxO3 optical beam deflectors

NASA Astrophysics Data System (ADS)

Imai, Tadayuki; Toyoda, Seiji; Miyazu, Jun; Kobayashi, Junya; Kojima, Seiji

2014-09-01

A space-charge-controlled optical beam deflector made of a KTa1-xNbxO3 (KTN) single crystal utilizes electrons that are injected through the cathode by applying voltage. With the deflector made of lithium-doped KTN (K0.95Li0.05Ta0.73Nb0.27O3, KLTN/0.05/0.27), we observed large increases in the capacitance of the deflector when we injected electrons. The increases were not caused by changes in the electrode interface but by changes in the permittivity of the bulk crystal. In the paraelectric phase, the KLTN/0.05/0.27 crystal exhibited nonlinearity in the dielectric response with double hysteresis loops in the D-E curves. We ascribed the permittivity change to this nonlinear phenomenon. We also discuss this nonlinearity in terms of the Landau-Devonshire phenomenological theory. The coefficient g4 of the fourth power term in the expanded free energy was negative in the paraelectric phase near the phase transition temperature as it is for other materials that exhibit a first-order phase transition. However, g4 depended on the temperature and its sign became positive about 15 °C above the phase transition temperature.

Virtual cathode microwave generator having annular anode slit

DOEpatents

Kwan, Thomas J. T.; Snell, Charles M.

1988-01-01

A microwave generator is provided for generating microwaves substantially from virtual cathode oscillation. Electrons are emitted from a cathode and accelerated to an anode which is spaced apart from the cathode. The anode has an annular slit therethrough effective to form the virtual cathode. The anode is at least one range thickness relative to electrons reflecting from the virtual cathode. A magnet is provided to produce an optimum magnetic field having the field strength effective to form an annular beam from the emitted electrons in substantial alignment with the annular anode slit. The magnetic field, however, does permit the reflected electrons to axially diverge from the annular beam. The reflected electrons are absorbed by the anode in returning to the real cathode, such that substantially no reflexing electrons occur. The resulting microwaves are produced with a single dominant mode and are substantially monochromatic relative to conventional virtual cathode microwave generators.

A Fully-Sealed Carbon-Nanotube Cold-Cathode Terahertz Gyrotron

PubMed Central

Yuan, Xuesong; Zhu, Weiwei; Zhang, Yu; Xu, Ningsheng; Yan, Yang; Wu, Jianqiang; Shen, Yan; Chen, Jun; She, Juncong; Deng, Shaozhi

2016-01-01

Gigahertz to terahertz radiation sources based on cold-cathode vacuum electron technology are pursued, because its unique characteristics of instant switch-on and power saving are important to military and space applications. Gigahertz gyrotron was reported using carbon nanotube (CNT) cold-cathode. It is reported here in first time that a fully-sealed CNT cold-cathode 0.22 THz-gyrotron is realized, typically with output power of 500 mW. To achieve this, we have studied mechanisms responsible for CNTs growth on curved shape metal surface, field emission from the sidewall of a CNT, and crystallized interface junction between CNT and substrate material. We have obtained uniform growth of CNTs on and direct growth from cone-cylinder stainless-steel electrode surface, and field emission from both tips and sidewalls of CNTs. It is essential for the success of a CNT terahertz gyrotron to have such high quality, high emitting performance CNTs. Also, we have developed a magnetic injection electron gun using CNT cold-cathode to exploit the advantages of such a conventional gun design, so that a large area emitting surface is utilized to deliver large current for electron beam. The results indicate that higher output power and higher radiation frequency terahertz gyrotron may be made using CNT cold-cathode electron gun. PMID:27609247

A Fully-Sealed Carbon-Nanotube Cold-Cathode Terahertz Gyrotron.

PubMed

Yuan, Xuesong; Zhu, Weiwei; Zhang, Yu; Xu, Ningsheng; Yan, Yang; Wu, Jianqiang; Shen, Yan; Chen, Jun; She, Juncong; Deng, Shaozhi

2016-09-09

Gigahertz to terahertz radiation sources based on cold-cathode vacuum electron technology are pursued, because its unique characteristics of instant switch-on and power saving are important to military and space applications. Gigahertz gyrotron was reported using carbon nanotube (CNT) cold-cathode. It is reported here in first time that a fully-sealed CNT cold-cathode 0.22 THz-gyrotron is realized, typically with output power of 500 mW. To achieve this, we have studied mechanisms responsible for CNTs growth on curved shape metal surface, field emission from the sidewall of a CNT, and crystallized interface junction between CNT and substrate material. We have obtained uniform growth of CNTs on and direct growth from cone-cylinder stainless-steel electrode surface, and field emission from both tips and sidewalls of CNTs. It is essential for the success of a CNT terahertz gyrotron to have such high quality, high emitting performance CNTs. Also, we have developed a magnetic injection electron gun using CNT cold-cathode to exploit the advantages of such a conventional gun design, so that a large area emitting surface is utilized to deliver large current for electron beam. The results indicate that higher output power and higher radiation frequency terahertz gyrotron may be made using CNT cold-cathode electron gun.

Screens and Displays.

ERIC Educational Resources Information Center

Edstrom, Malin

1987-01-01

Discusses the characteristics of different computer screen technologies including the possible harmful effects on health of cathode ray tube (CRT) terminals. CRT's are compared to other technologies including liquid crystal displays, plasma displays, electroluminiscence displays, and light emitting diodes. A chart comparing the different…

High performance platinum single atom electrocatalyst for oxygen reduction reaction

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

Liu, Jing; Jiao, Menggai; Lu, Lanlu

For the large-scale sustainable implementation of polymer electrolyte membrane fuel cells in vehicles, high-performance electrocatalysts with low platinum consumption are desirable for use as cathode material during the oxygen reduction reaction in fuel cells. Here we report a carbon black-supported cost-effective, efficient and durable platinum single-atom electrocatalyst with carbon monoxide/methanol tolerance for the cathodic oxygen reduction reaction. The acidic single-cell with such a catalyst as cathode delivers high performance, with power density up to 680 mW cm –2 at 80 °C with a low platinum loading of 0.09 mgPt cm –2, corresponding to a platinum utilization of 0.13 gPt kWmore » –1 in the fuel cell. Good fuel cell durability is also observed. As a result, theoretical calculations reveal that the main effective sites on such platinum single-atom electrocatalysts are single-pyridinic-nitrogen-atom-anchored single-platinum-atom centres, which are tolerant to carbon monoxide/methanol, but highly active for the oxygen reduction reaction.« less

High performance platinum single atom electrocatalyst for oxygen reduction reaction

DOE PAGES

Liu, Jing; Jiao, Menggai; Lu, Lanlu; ...

2017-07-24

For the large-scale sustainable implementation of polymer electrolyte membrane fuel cells in vehicles, high-performance electrocatalysts with low platinum consumption are desirable for use as cathode material during the oxygen reduction reaction in fuel cells. Here we report a carbon black-supported cost-effective, efficient and durable platinum single-atom electrocatalyst with carbon monoxide/methanol tolerance for the cathodic oxygen reduction reaction. The acidic single-cell with such a catalyst as cathode delivers high performance, with power density up to 680 mW cm –2 at 80 °C with a low platinum loading of 0.09 mgPt cm –2, corresponding to a platinum utilization of 0.13 gPt kWmore » –1 in the fuel cell. Good fuel cell durability is also observed. As a result, theoretical calculations reveal that the main effective sites on such platinum single-atom electrocatalysts are single-pyridinic-nitrogen-atom-anchored single-platinum-atom centres, which are tolerant to carbon monoxide/methanol, but highly active for the oxygen reduction reaction.« less

A Host-Configured Lithium-Sulfur Cell Built on 3D Nickel Photonic Crystal with Superior Electrochemical Performances.

PubMed

Lin, Shengxuan; Yan, Yang; Cai, Zihe; Liu, Lin; Hu, Xiaobin

2018-04-18

The insulator of the sulfur cathode and the easy dendrites growth of the lithium anode are the main barriers for lithium-sulfur cells in commercial application. Here, a 3D NPC@S/3D NPC@Li full cell is reported based on 3D hierarchical and continuously porous nickel photonic crystal (NPC) to solve the problems of sulfur cathode and lithium anode at the same time. In this case, the 3D NPC@S cathode can not only offer a fast transfer of electron and lithium ion, but also effectively prevent the dissolution of polysulfides and the tremendous volume change during cycling, and the 3D NPC@Li anode can efficiently inhibit the growth of lithium dendrites and volume expansion, too. As a result, the cell exhibits a high reversible capacity of 1383 mAh g -1 at 0.5 C (the current density of 837 mA g -1 ), superior rate ability (the reversible capacity of 735 mAh g -1 at the extremely high current density of 16 750 mA g -1 ) with excellent coulombic efficiency of about 100% and an excellent cycle life over 500 cycles with only about 0.026% capacity loss per cycle. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High Performance Proton-Conducting Solid Oxide Fuel Cells with a Layered Perovskite GdBaCuCoO5+ x Cathode

NASA Astrophysics Data System (ADS)

Zhang, Xiaozhen; Jiang, Yuhua; Hu, Xuebing; Sun, Liangliang; Ling, Yihan

2018-03-01

Proton-conducting solid oxide fuel cell (H-SOFC) based on layered perovskite type GdBaCuCoO5+x (GBCC) cathode was fabricated with in situ drop-coating BaZr0.1Ce0.7Y0.2O3-δ (BZCY) electrolyte membrane. The influences of Cu doping into Co sites of GdBaCo2O5+ x on the electrical conductivity and conduction mechanism, thermal expansion property and electrochemical performance of cathode materials and corresponding single cell were investigated. Results show that the electrical conductivity decreased and the conduction mechanism would gradually transform to the semiconductor-like behavior. A high maximum power density of 480 mW cm-2 was obtained for the anode supported NiO-BZCY/NiO-BZCY/BZCY/GBCC single cells with wet H2 fuel at 700 °C. The corresponding polarization resistance was as low as 0.17 Ω cm2. The excellent electrochemical performance of as-prepared single cell indicates that GBCC is a good candidate of cathode materials for H-SOFCs.

Multi-variable mathematical models for the air-cathode microbial fuel cell system

NASA Astrophysics Data System (ADS)

Ou, Shiqi; Kashima, Hiroyuki; Aaron, Douglas S.; Regan, John M.; Mench, Matthew M.

2016-05-01

This research adopted the version control system into the model construction for the single chamber air-cathode microbial fuel cell (MFC) system, to understand the interrelation of biological, chemical, and electrochemical reactions. The anodic steady state model was used to consider the chemical species diffusion and electric migration influence to the MFC performance. In the cathodic steady state model, the mass transport and reactions in a multi-layer, abiotic cathode and multi-bacteria cathode biofilm were simulated. Transport of hydroxide was assumed for cathodic pH change. This assumption is an alternative to the typical notion of proton consumption during oxygen reduction to explain elevated cathode pH. The cathodic steady state model provided the power density and polarization curve performance results that can be compared to an experimental MFC system. Another aspect considered was the relative contributions of platinum catalyst and microbes on the cathode to the oxygen reduction reaction (ORR). Simulation results showed that the biocatalyst in a cathode that includes a Pt/C catalyst likely plays a minor role in ORR, contributing up to 8% of the total power calculated by the models.

Study of electrode pattern design for a CZT-based PET detector.

PubMed

Gu, Y; Levin, C S

2014-06-07

We are developing a 1 mm resolution small animal positron emission tomography (PET) system using 3D positioning cadmium zinc telluride photon detectors comprising 40 mm × 40 mm × 5 mm crystals metalized with a cross-strip electrode pattern with a 1 mm anode strip pitch. We optimized the electrode pattern design for intrinsic sensitivity and spatial, energy and time resolution performance using a test detector comprising cathode and steering electrode strips of varying dimensions. The study found 3 and 5 mm width cathode strips locate charge-shared photon interactions near cathode strip boundaries with equal precision. 3 mm width cathode strips exhibited large time resolution variability as a function of photon interaction location between the anode and cathode planes (~26 to ~127.5 ns full width at half maximum (FWHM) for 0.5 mm and 4.2 mm depths, respectively). 5 mm width cathode strips by contrast exhibited more stable time resolution for the same interaction locations (~34 to ~83 ns FWHM), provided more linear spatial positioning in the direction orthogonal to the electrode planes, and as much as 68.4% improvement in photon sensitivity over the 3 mm wide cathode strips. The results were understood by analyzing the cathode strips' weighting functions, which indicated a stronger 'small pixel' effect in the 3 mm wide cathode strips. Photon sensitivity and anode energy resolution were seen to improve with decreasing steering electrode bias from 0 to -80 V w.r.t. the anode potential. A slight improvement in energy resolution was seen for wider steering electrode strips (400 versus 100 µm) for charge-shared photon interactions. Although this study successfully focused on electrode pattern features for PET performance, the results are generally applicable to semiconductor photon detectors employing cross-trip electrode patterns.

Study of electrode pattern design for a CZT-based PET detector

PubMed Central

Gu, Y; Levin, C S

2014-01-01

We are developing a 1 mm resolution small animal positron emission tomography (PET) system using 3-D positioning Cadmium Zinc Telluride (CZT) photon detectors comprising 40 mm × 40 mm × 5 mm crystals metalized with a cross-strip electrode pattern with a 1 mm anode strip pitch. We optimized the electrode pattern design for intrinsic sensitivity and spatial, energy and time resolution performance using a test detector comprising cathode and steering electrode strips of varying dimensions. The study found 3 mm and 5 mm width cathode strips locate charge-shared photon interactions near cathode strip boundaries with equal precision. 3 mm width cathode strips exhibited large time resolution variability as a function of photon interaction location between the anode and cathode planes (~26 ns to ~127.5 ns FWHM for 0.5 mm and 4.2 mm depths, respectively). 5 mm width cathode strips by contrast exhibited more stable time resolution for the same interaction locations (~34 ns to ~83 ns FWHM), provided more linear spatial positioning in the direction orthogonal to the electrode planes, and as much as 68.4% improvement in photon sensitivity over the 3 mm wide cathode strips. The results were understood by analyzing the cathode strips’ weighting functions, which indicated a stronger “small pixel” effect in the 3 mm wide cathode strips. Photon sensitivity and anode energy resolution were seen to improve with decreasing steering electrode bias from 0 V to −80 V w.r.t the anode potential. A slight improvement in energy resolution was seen for wider steering electrode strips (400 μm vs. 100 μm) for charge-shared photon interactions. Although this study successfully focused on electrode pattern features for PET performance, the results are generally applicable to semiconductor photon detectors employing cross-trip electrode patterns. PMID:24786208

Enhancing the performance of single-chambered microbial fuel cell using manganese/palladium and zirconium/palladium composite cathode catalysts.

PubMed

Jadhav, Dipak A; Deshpande, Parag A; Ghangrekar, Makarand M

2017-08-01

Application of ZrO 2 , MnO 2 , palladium, palladium-substituted-zirconium oxide (Zr 0.98 Pd 0.02 O 2 ) and palladium-substituted-manganese oxide (Mn 0.98 Pd 0.02 O 2 ) cathode catalysts in a single-chambered microbial fuel cell (MFC) was explored. The highest power generation (1.28W/m 3 ) was achieved in MFC with Mn 0.98 Pd 0.02 O 2 catalyst, which was higher than that with MnO 2 (0.58W/m 3 ) alone; whereas, MFC having Zr 0.98 Pd 0.02 O 2 catalyzed cathode and non-catalyzed cathode produced powers of 1.02 and 0.23W/m 3 , respectively. Also, low-cost zirconium-palladium-composite showed better catalytic activity and capacitance over ZrO 2 with 20A/m 3 current production and demonstrated its suitability for MFC applications. Cyclic voltammetry analyses showed higher well-defined redox peaks in composite catalysts (Mn/Zr-Pd-C) over other catalyzed MFCs containing MnO 2 or ZrO 2 . Electrochemical behaviour of composite catalysts on cathode showed higher availability of adsorption sites for oxygen reduction and, hence, enhanced the rate of cathodic reactions. Thus, Mn/Zr-Pd-C-based composite catalysts exhibited superior cathodic performance and could be proposed as alternatives to costly Pd-catalyst for field applications. Copyright © 2017 Elsevier Ltd. All rights reserved.

Performance evaluation of Mn and Fe doped SrCo0.9Nb0.1O3-δ cathode for IT-SOFC application

NASA Astrophysics Data System (ADS)

Bele, Lokesh; Lenka, R. K.; Patro, P. K.; Muhmood, L.; Mahata, T.; Sinha, P. K.

2018-02-01

Cathode materials of Mn and Fe doped SrCo0.9Nb0.1O3-δ, are synthesized by solid state route for intermediate temperature fuel cell applications. Phase pure material is obtained after calcining the precursors at 1100 °C. Phase compatibility is observed between this novel cathode material with gadolinia doped ceria (GDC) electrolyte material as reflected in the diffraction pattern. The state of art YSZ electrolyte is not compatible with this cathode material. Average thermal expansion coefficient of the material varies between 17 to 22 X 10-6 K-1 on doping, from room temperature to 800 °C. Increase in thermal expansion coefficient is observed with Mn and Fe doping associated with the loss of oxygen from the crystal. The electrical conductivity of the cathode material decreases with Fe and Mn doping. Mn doped samples show lowest conductivity. From the symmetric cell measurement lower area specific resistance (0.16 Ω-cm2) is obtained for un-doped samples, at 850 °C. From the initial results it can be inferred that Mn/Fe doping improves neither the thermal expansion co-efficient nor the electrochemical activity.

X-ray Crystal Truncation Rod Studies of Surface Oxidation and Reduction on Pt(111)

DOE PAGES

Liu, Yihua; Barbour, Andi; Komanicky, Vladimir; ...

2016-02-26

Here, we present X-ray crystal truncation rods measurements of Pt(111) surface under electrochemical conditions. Analyses of crystal truncation rods reveal that surface oxide formation buckles the top surface layer of platinum to two different heights at the potential (0.95 V vs RHE) below the so-called place-exchange potential. While the anti-Bragg intensity, sensitive to the top surface layer, drops in response to the anodic charge transfers, its responses to the cathodic charge transfers are significantly delayed. Implications to the surface oxidation and reduction behaviors are discussed.

Cathodic electrodeposition of mixed molybdenum tungsten oxides from peroxo-polymolybdotungstate solutions.

PubMed

Kondrachova, Lilia; Hahn, Benjamin P; Vijayaraghavan, Ganesh; Williams, Ryan D; Stevenson, Keith J

2006-12-05

Mixed molybdenum tungsten trioxide films of varying stoichiometry (MoxW1 - xO3, 0 < x < 1) were prepared by cathodic electrodeposition on indium tin oxide (ITO)-coated glass substrates from aqueous peroxo-polymolybdotungstate solutions. Electrochemical quartz crystal microbalance (EQCM), cyclic voltammetry, and chronocoulometry were used to gain insight into the electrodeposition mechanism. The compositional and structural properties were characterized for MoxW1 - xO3 films deposited at intermediate potentials (-0.35 V vs Ag/AgCl) and sintered at 250 degrees C using energy-dispersive spectroscopy, X-ray diffraction, and Raman spectroscopy. These studies reveal that films consist of homogeneously mixed MoxW1 - xO3, with an enriched Mo content ranging in composition from 0.4 < x < 0.7 depending upon the mol % Mo present in the deposition solution. Chronoamperometry and spectroelectrochemical measurements were conducted to estimate lithium ion diffusion coefficients and coloration efficiencies for the mixed metal oxide films in 1 M LiClO4/propylene carbonate. The subtle interplay between structural and compositional properties due to the uniform mixing of Mo and W oxide components shows that electrochromic and lithium ion transport properties are moderately enhanced relative to those of single-component WO3 and MoO3 and demonstrate improved structural stability over pure MoO3 polymorphs during electrochemical cycling.

Calcium cation enhanced cathode/electrolyte interface property of Li2FeSiO4/C cathode for lithium-ion batteries with long-cycling life

NASA Astrophysics Data System (ADS)

Qu, Long; Li, Mingtao; Tian, Xiaolu; Liu, Pei; Yi, Yikun; Yang, Bolun

2018-03-01

Currently, the cycle performance at low rate is one of the most critical factor for realizing practical applications of Li2FeSiO4/C as a cathode of the lithium-ion batteries. To meet this challenge, calcium (Ca)-doped Li2FeSiO4/C is prepared by using the sol-gel method with soluble Li, Fe, Si and Ca sources. X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy and X-ray photoelectron spectroscopy measurements are carried out to determine the crystal structures, morphologies, particle sizes and chemical valence states of the resulting products. Rietveld refinement confirms that Ca-doped Li2FeSiO4 has a monoclinic P21/n structure and that a Ca cation occupies the Fe site in the Li2FeSiO4 lattice. The grain size of Ca-doped Li2FeSiO4 is approximately 20 nm and the nanoparticles are interconnected tightly with amorphous carbon layer. As a cathode material for the lithium-ion batteries, Li2Fe0.97Ca0.03SiO4/C delivers a high discharge capacity of 186 mAh g-1 at a 0.5 C rate. Its capacity retention after the 100th cycle reaches 87%, which increases by 25 percentage points compared with Li2FeSiO4/C. The Li2Fe0.97Ca0.03SiO4/C cathode exhibits good rate performance, with corresponding discharge capacities of 170, 157, 144 and 117 mAh g-1 at 1 C, 2 C, 5 C and 10 C rates, respectively. In summary, the improvement of the electrochemical performance can be attributed to a coefficient of the strengthened crystal structure stability during Li+ deintercalation-intercalation and restrained side reactions between electrode and electrolyte.

Microwave generator

DOEpatents

Kwan, T.J.T.; Snell, C.M.

1987-03-31

A microwave generator is provided for generating microwaves substantially from virtual cathode oscillation. Electrons are emitted from a cathode and accelerated to an anode which is spaced apart from the cathode. The anode has an annular slit there through effective to form the virtual cathode. The anode is at least one range thickness relative to electrons reflecting from the virtual cathode. A magnet is provided to produce an optimum magnetic field having the field strength effective to form an annular beam from the emitted electrons in substantial alignment with the annular anode slit. The magnetic field, however, does permit the reflected electrons to axially diverge from the annular beam. The reflected electrons are absorbed by the anode in returning to the real cathode, such that substantially no reflexing electrons occur. The resulting microwaves are produced with a single dominant mode and are substantially monochromatic relative to conventional virtual cathode microwave generators. 6 figs.

Insight into self-discharge of layered lithium-rich oxide cathode in carbonate-based electrolytes with and without additive

NASA Astrophysics Data System (ADS)

Li, Jianhui; Xing, Lidan; Zhang, Liping; Yu, Le; Fan, Weizhen; Xu, Mengqing; Li, Weishan

2016-08-01

Self-discharge behavior of layered lithium-rich oxide as cathode of lithium ion battery in a carbonated-based electrolyte is understood, and a simple boron-containing compound, trimethyl borate (TMB), is used as an electrolyte additive to suppress this self-discharge. It is found that layered lithium-rich oxide charged under 4.8 V in additive-free electrolyte suffers severe self-discharge and TMB is an effective electrolyte additive for self-discharge suppression. Physical characterizations from XRD, SEM, TEM, XPS and ICP-MS demonstrate that the crystal structure of the layered lithium-rich oxide collapses due to the chemical interaction between the charged oxide and electrolyte. When TMB is applied, the structural integrity of the oxide is maintained due to the protective cathode film generated from the preferential oxidation of TMB.

Hollow - cathode electrode for high-power, high-pressure discharge devices

DOEpatents

Chang, Jim J.; Alger, Terry W.

1995-01-01

Several different cold cathode configurations for a gas discharge device each having a plurality of grooves of selected spacing, depth and width to improve the emission of electrons in a gas discharge device. Each of the cold cathode configurations can be machined from a single piece of a selected material. Several of the configurations can be assembled with individual elements which is easily seen from the various figures.

Surface Alloying of SUS 321 Chromium-Nickel Steel by an Electron-Plasma Process

NASA Astrophysics Data System (ADS)

Ivanov, Yu. F.; Teresov, A. D.; Petrikova, E. A.; Krysina, O. V.; Ivanova, O. V.; Shugurov, V. V.; Moskvin, P. V.

2017-07-01

The mechanisms of forming nanostructured, nanophase layers are revealed and analyzed in austenitic steel subjected to surface alloying using an electron-plasma process. Nanostructured, nanophase layers up to 30 μm in thickness were formed by melting of the film/substrate system with an electron beam generated by a SOLO facility (Institute of High Current Electronics, SB RAS), Tomsk), which ensured crystallization and subsequent quenching at the cooling rates within the range 105-108 K/s. The surface was modified with structural stainless steel specimens (SUS 321 steel). The film/substrate system (film thickness 0.5 μm) was formed by a plasma-assisted vacuum-arc process by evaporating a cathode made from a sintered pseudoalloy of the following composition: Zr - 6 at.% Ti - 6 at.% Cu. The film deposition was performed in a QUINTA facility equipped with a PINK hot-cathode plasma source and DI-100 arc evaporators with accelerated cooling of the process cathode, which allowed reducing the size and fraction of the droplet phase in the deposited film. It is found that melting of the film/substrate system (Zr-Ti-Cu)/(SUS 321 steel) using a high-intensity pulsed electron beam followed by the high-rate crystallization is accompanied by the formation of α-iron cellular crystallization structure and precipitation of Cr2Zr, Cr3C2 and TiC particles on the cell boundaries, which as a whole allowed increasing microhardness by a factor of 1.3, Young's modulus - by a factor of 1.2, wear resistance - by a factor of 2.7, while achieving a three-fold reduction in the friction coefficient.

Study on structural refinement and electrochemical behaviour of Ba0.5Sr0.5Co0.8Fe0.2O3-δ as cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFC)

NASA Astrophysics Data System (ADS)

Kautkar, Pranay R.; Shirbhate, Shraddha C.; Acharya, Smita A.

2018-05-01

Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) was prepared by ethylene glycol-citrate combined sol-gel combustion route and calcined at optimized temperature 1050°C. The X-ray Diffraction (XRD) data revealing the crystal purity of BSCF cathode was refined by the Cubic-type structure having the space group Pm-3m by Rietveld analysis. Refined lattice parameter of BSCF cathode is a = 3.9759 Å and unit cell volume is 62.85 (4) Å3, Co/Fe-O bond length from VESTA program figured out to be 1.987 (3) Å. Electron density distribution (EDD) of the unit cell of BSCF cathode shows the bonding feature with oxygen ions, this could represent oxygen vacancies are present in the lattice. These results reflected in electrochemical impedance spectra measurement of symmetric cell. Area of specific resistance (ASR) of the BSCF cathode was found to be 0.17 Ω.cm2 at 700°C and respective activation energy (Ea) 1.15 eV. It shows surface exchange at cathode interface, surface diffusion and self-diffusion happened through Ce0.85Sd0.15O1.95 (SDC15) electrolyte.

Synthesis of lithium nickel cobalt manganese oxide cathode materials by infrared induction heating

NASA Astrophysics Data System (ADS)

Hsieh, Chien-Te; Chen, Yu-Fu; Pai, Chun-Ting; Mo, Chung-Yu

2014-12-01

This study adopts an in-situ infrared (IR) sintering incorporated with carbonization technique to synthesize carbon-coated LiNi1/3Co1/3Mn1/3O2 (LNCM) cathode materials for Li-ion batteries. Compared with electric resistance heating, the in-situ IR sintering is capable of rapidly producing highly-crystalline LNCM powders at 900 °C within a short period, i.e., 3 h in this case. Glucose additive is employed to serve a carbon precursor, which is carbonized and coated over the surface of LNCM crystals during the IR sintering process. The electrochemical performance of LNCM cathodes is well examined by charge-discharge cycling at 0.1-5C. An appropriate carbon coating is capable of raising discharge capacity (i.e., 181.5 mAh g-1 at 0.1C), rate capability (i.e., 75.0 mAh g-1 at 5C), and cycling stability (i.e., capacity retention: 94.2% at 1C after 50 cycles) of LNCM cathodes. This enhanced performance can be ascribed to the carbon coating onto the external surface of LNCM powders, creating an outer circuit of charge-transfer pathway and preventing cathode corrosion from direct contact to the electrolyte. Accordingly, the in-situ IR sintering technique offers a potential feasibility for synthesizing cathode materials commercially in large scale.

A design of a PET detector using micro-channel plate photomultipliers with transmission-line readout

NASA Astrophysics Data System (ADS)

Kim, H.; Frisch, H.; Chen, C.-T.; Genat, J.-F.; Tang, F.; Moses, W. W.; Choong, W. S.; Kao, C.-M.

2010-10-01

A computer simulation study has been conducted to investigate the feasibility of a positron emission tomography (PET) detector design by using micro-channel plate (MCP) photomultiplier tubes (PMT) with transmission-line (TL) readout and waveform sampling. The detector unit consisted of a 24×24 array of pixelated LSO crystals, each of which was 4×4×25 mm 3 in size, and two 102×102 mm 2 MCP-PMTs coupled to both sides of the scintillator array. The crystal (and TL) pitch was 4.25 mm and reflective medium was inserted between the crystals. The transport of the optical photons inside the scintillator were simulated by using the Geant4 package. The output pulses of the MCP-PMT/TL unit were formed by applying the measured single photo-electron response of the MCP-PMT/TL unit to each individual photon that interacts with the photo-cathode of the MCP-PMT. The waveforms of the pulses at both ends of the TL strips were measured and analyzed to produce energy and timing information for the detected event. An experimental setup was developed by employing a Photonis Planacon MCP-PMT (XP85022) and a prototype TL board for measuring the single photo-electron response of the MCP-PMT/TL. The simulation was validated by comparing the predicted output pulses to measurements obtained with a single MCP-PMT/TL coupled to an LSO crystal exposed to 511 keV gamma rays. The validated simulation was then used to investigate the performance of the proposed new detector design. Our simulation result indicates an energy resolution of ˜11% at 511 keV. When using a 400-600 keV energy window, we obtain a coincidence timing resolution of ˜323 ps FWHM and a coincidence detection efficiency of ˜40% for normally incident 511 keV photons. For the positioning accuracy, it is determined by the pitch of the TLs (and crystals) in the direction normal to the TLs and measured to be ˜2.5 mm in the direction parallel to the TLs. The energy and timing obtained at the front- and back-end of the scintillator array also show differences that are correlated with the depth of interaction of the event.

A Design of a PET Detector Using Micro-Channel Plate Photomultipliers with Transmission-Line Readout.

PubMed

Kim, H; Frisch, H; Chen, C-T; Genat, J-F; Tang, F; Moses, W W; Choong, W S; Kao, C-M

2010-01-01

A computer simulation study has been conducted to investigate the feasibility of a positron emission tomography (PET) detector design by using micro-channel plate (MCP) photomultiplier tubes (PMT) with transmission-line (TL) read-out and waveform sampling. The detector unit consisted of a 24×24 array of pixelated LSO crystals, each of which was 4×4×25 mm(3) in size, and two 102×102 mm(2) MCP-PMTs coupled to both sides of the scintillator array. The crystal (and TL) pitch was 4.25 mm and reflective medium was inserted between the crystals. The transport of the optical photons inside the scintillator were simulated by using the Geant4 package. The output pulses of the MCP-PMT/TL unit were formed by applying the measured single photo-electron response of the MCP-PMT/TL unit to each individual photon that interacts with the photo-cathode of the MCP-PMT. The waveforms of the pulses at both ends of the TL strips were measured and analyzed to produce energy and timing information for the detected event. An experimental setup was developed by employing a Photonis Planacon MCP-PMT (XP85022) and a prototype TL board for measuring the single photo-electron response of the MCP-PMT/TL. The simulation was validated by comparing the predicted output pulses to measurements obtained with a single MCP-PMT/TL coupled to an LSO crystal exposed to 511 keV gamma rays. The validated simulation was then used to investigate the performance of the proposed new detector design. Our simulation result indicates an energy resolution of ~11% at 511 keV. When using a 400-600 keV energy window, we obtain a coincidence timing resolution of ~323 ps FWHM and a coincidence detection efficiency of ~40% for normally-incident 511keV photons. For the positioning accuracy, it is determined by the pitch of the TLs (and crystals) in the direction normal to the TLs and measured to be ~2.5 mm in the direction parallel to the TLs. The energy and timing obtained at the front- and back-end of the scintillator array also show differences that are correlated with the depth of interaction of the event.

Diagnostics and Degradation Investigations of Li-Ion Battery Electrodes using Single Nanowire Electrochemical Cells

NASA Astrophysics Data System (ADS)

Palapati, Naveen Kumar Reddy

Portable energy storage devices, which drive advanced technological devices, are improving the productivity and quality of our everyday lives. In order to meet the growing needs for energy storage in transportation applications, the current lithium-ion (Li-ion) battery technology requires new electrode materials with performance improvements in multiple aspects: (1) energy and power densities, (2) safety, and (3) performance lifetime. While a number of interesting nanomaterials have been synthesized in recent years with promising performance, accurate capabilities to probe the intrinsic performance of these high-performance materials within a battery environment are lacking. Most studies on electrode nanomaterials have so far used traditional, bulk-scale techniques such as cyclic voltammetry, electrochemical impedance spectroscopy, and Raman spectroscopy. These approaches give an ensemble-average estimation of the electrochemical properties of a battery electrode and does not provide a true indication of the performance that is intrinsic to its material system. Thus, new techniques are essential to understand the changes happening at a single particle level during the operation of a battery. The results from this thesis solve this need and study the electrical, mechanical and size changes that take place in a battery electrode at a single particle level. Single nanowire lithium cells are built by depositing nanowires in carefully designed device regions of a silicon chip using Dielectrophoresis (DEP). This work has demonstrated the assembly of several NW cathode materials like LiFePO 4, pristine and acid-leached alpha-MnO2, todorokite - MnO2, acid and nonacid-leached Na0.44MnO2. Within these materials, alpha-MnO2 was chosen as the model material system for electrochemical experiments. Electrochemical lithiation of pristine alpha-MnO 2 was performed inside a glove box. The volume, elasticity and conductivity changes were measured at each state-of-charge (SOC) to understand the performance of the material system. The NW size changes due to lithiation were measured using an Atomic Force Microscope (AFM) in the tapping mode. Electronic conductivity changes as a function of lithiation was also studied in the model alpha-MnO 2 NWs and was found to decrease substantially with lithium loading. In other measurements involving a comparison between the alpha and todorokite phases of this material system, it was observed that the rate capability of these materials is limited not by the electronic but, by the ionic conductivity. Mechanical degradation of a battery cathode represents an important failure mode, which results in an irreversible loss of capacity with cycling. To analyze and understand these degradation mechanisms, this thesis has tested the evolution of nanomechanical properties of a battery cathode. Specifically, contact-mode AFM measurements have focused on the SOC-dependent changes in the Young's modulus and fracture strength of an alpha-MnO2 NW electrode, which are critical parameters that determine its mechanical stability. These changes have been studied at the end of the first discharge step, 1 full electrochemical cycle, and 20 cycles. The observations show an increase in Young's modulus at low concentrations of lithium loading and this is attributed to the formation of new Li-O bonds within the tunnel-structured cathode. As the lithium loading increases further, the Young's modulus was observed to reduce and this is hypothesized to occur due to the distortions of the crystal at high lithium concentrations. The experimental-to-theoretical fracture strength ratio, which points to the defect density in the crystal at a given stoichiometry, was observed to reduce with electrochemical lithium insertion / cycling. This capability has demonstrated lithiation-dependent mechanical property measurements for the first time and represents an important contribution since degradation models, which are currently in use for materials at any size scale, always assume constant values regardless of the change in stoichiometry.

Electrochemical Induced Calcium Phosphate Precipitation: Importance of Local pH

PubMed Central

2017-01-01

Phosphorus (P) is an essential nutrient for living organisms and cannot be replaced or substituted. In this paper, we present a simple yet efficient membrane free electrochemical system for P removal and recovery as calcium phosphate (CaP). This method relies on in situ formation of hydroxide ions by electro mediated water reduction at a titanium cathode surface. The in situ raised pH at the cathode provides a local environment where CaP will become highly supersaturated. Therefore, homogeneous and heterogeneous nucleation of CaP occurs near and at the cathode surface. Because of the local high pH, the P removal behavior is not sensitive to bulk solution pH and therefore, efficient P removal was observed in three studied bulk solutions with pH of 4.0 (56.1%), 8.2 (57.4%), and 10.0 (48.4%) after 24 h of reaction time. While P removal efficiencies are not generally affected by bulk solution pH, the chemical-physical properties of CaP solids collected on the cathode are still related to bulk solution pH, as confirmed by structure characterizations. High initial solution pH promotes the formation of more crystalline products with relatively high Ca/P molar ratio. The Ca/P molar ratio increases from 1.30 (pH 4.0) to 1.38 (pH 8.2) and further increases to 1.55 (pH 10.0). The formation of CaP precipitates was a typical crystallization process, with an amorphous phase formed at the initial stage which then transforms to the most stable crystal phase, hydroxyapatite, which is inferred from the increased Ca/P molar ratio from 1.38 (day 1) to the theoretical 1.76 (day 11) and by the formation of needle-like crystals. Finally, we demonstrated the efficiency of this system for real wastewater. This, together with the fact that the electrochemical method can work at low bulk pH, without dosing chemicals and a need for a separation process, highlights the potential application of the electrochemical method for P removal and recovery. PMID:28872838

Multi-variable mathematical models for the air-cathode microbial fuel cell system

DOE PAGES

Ou, Shiqi; Kashima, Hiroyuki; Aaron, Douglas S.; ...

2016-03-10

This research adopted the version control system into the model construction for the single chamber air-cathode microbial fuel cell (MFC) system, to understand the interrelation of biological, chemical, and electrochemical reactions. The anodic steady state model was used to consider the chemical species diffusion and electric migration influence to the MFC performance. In the cathodic steady state model, the mass transport and reactions in a multi-layer, abiotic cathode and multi-bacteria cathode biofilm were simulated. Transport of hydroxide was assumed for cathodic pH change. This assumption is an alternative to the typical notion of proton consumption during oxygen reduction to explainmore » elevated cathode pH. The cathodic steady state model provided the power density and polarization curve performance results that can be compared to an experimental MFC system. Another aspect we considered was the relative contributions of platinum catalyst and microbes on the cathode to the oxygen reduction reaction (ORR). We found simulation results showed that the biocatalyst in a cathode that includes a Pt/C catalyst likely plays a minor role in ORR, contributing up to 8% of the total power calculated by the models.« less

Oxygen-consuming chlor alkali cell configured to minimize peroxide formation

DOEpatents

Chlistunoff, Jerzy B [Los Alamos, NM; Lipp, Ludwig [Brookfield, CT; Gottesfeld, Shimshon [Niskayuna, NY

2006-08-01

Oxygen-consuming zero gap chlor-alkali cell was configured to minimize peroxide formation. The cell included an ion-exchange membrane that divided the cell into an anode chamber including an anode and a cathode chamber including an oxygen gas diffusion cathode. The cathode included a single-piece of electrically conducting graphitized carbon cloth. Catalyst and polytetrafluoroethylene were attached to only one side of the cloth. When the cathode was positioned against the cation exchange membrane with the catalyst side away from the membrane, electrolysis of sodium chloride to chlorine and caustic (sodium hydroxide) proceeded with minimal peroxide formation.

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

Majzoobi, A.; Joshi, R. P., E-mail: ravi.joshi@ttu.edu; Neuber, A. A.

Particle-in-cell simulations are performed to analyze the efficiency, output power and leakage currents in a 12-Cavity, 12-Cathode rising-sun magnetron with diffraction output (MDO). The central goal is to conduct a parameter study of a rising-sun magnetron that comprehensively incorporates performance enhancing features such as transparent cathodes, axial extraction, the use of endcaps, and cathode extensions. Our optimum results demonstrate peak output power of about 2.1 GW, with efficiencies of ∼70% and low leakage currents at a magnetic field of 0.45 Tesla, a 400 kV bias with a single endcap, for a range of cathode extensions between 3 and 6 centimeters.

Organic-Inorganic Hybrid Interfacial Layer for High-Performance Planar Perovskite Solar Cells.

PubMed

Yang, Hao; Cong, Shan; Lou, Yanhui; Han, Liang; Zhao, Jie; Sun, Yinghui; Zou, Guifu

2017-09-20

4,7-Diphenyl-1,10-phenanthroline (Bphen) is an efficient electron transport and hole blocking material in organic photoelectric devices. Here, we report cesium carbonate (Cs 2 CO 3 ) doped Bphen as cathode interfacial layer in CH 3 NH 3 PbI 3-x Cl x based planar perovskite solar cells (PSCs). Investigation finds that introducing Cs 2 CO 3 suppresses the crystallization of Bphen and benefits a smooth interface contact between the perovskite and electrode, resulting in the decrease in carrier recombination and the perovskite degradation. In addition, the matching energy level of Bphen film in the PSCs effectively blocks the holes diffusion to cathode. The resultant power conversion efficiency (PCE) achieves as high as 17.03% in comparison with 12.67% of reference device without doping. Besides, experiments also demonstrate the stability of PSCs have large improvement because the suppressed crystallization of Bphen by doping Cs 2 CO 3 as a superior barrier layer blocks the Ag atom and surrounding moisture access to the vulnerable perovskite layer.

Redox potential trend with transition metal elements in lithium-ion battery cathode materials

NASA Astrophysics Data System (ADS)

Chen, Zhenlian; Li, Jun

2013-03-01

First-principles calculations are performed to investigate the relationship between the intrinsic voltage and element-lattice for the popular transition metal oxides and polyoxyanionic compounds as cathode materials for lithium-ion batteries. A V-shape redox potential in olivine phosphates LiMPO4 and orthogonal silicates Li2MSiO4 (M =Mn, Fe, Co, Ni), and an N-shape one in layered oxides LiMO2 (M =Mn, Fe, Co, Ni, Cu) relative to transition metal M elements are found to be inversely characteristic of electronic energy contribution, which costs energy in the lithiation process and is defined as electron affinity. The maxima of electron affinity, locating at different elements for different types of crystal lattices are determined by delectronic configurations that cross the turning point of a full occupancy of electronic bands, which is determined by the cooperative effect of crystal field splitting and intraionic exchange interactions. The Ningbo Key Innovation Team, National Natural Science Foundation of China, Postdoctoral Foundation of China

[Newly developed monitor for IVR: liquid crystal display (LCD) replaced with cathode ray tube (CRT)].

PubMed

Ichida, Takao; Hosogai, Minoru; Yokoyama, Kouji; Ogawa, Takayoshi; Okusako, Kenji; Shougaki, Masachika; Masai, Hironao; Yamada, Eiji; Okuyama, Kazuo; Hatagawa, Masakatsu

2004-09-01

For physicians who monitor images during interventional radiology (VR), we have built and been using a system that employs a liquid crystal display (LCD) instead of the conventional cathode ray tube (CRT). The system incorporates a ceiling-suspension-type monitor (three-display monitor) with an LCD on each of the three displays for the head and abdominal regions and another ceiling-suspension-type monitor (5-display monitor) with an LCD on each display for the cardiac region. As these monitors are made to be thin and light in weight, they can be placed in a high position in the room, thereby saving space and allowing for more effective use of space in the X-ray room. The system has also improved the efficiency of operators in the IVR room. The three-display folding mechanism allows the displays to be viewed from multiple directions, thereby improving the environment so that the performance of IVR can be observed.

Sodium intercalation in the phosphosulfate cathode NaFe2(PO4)(SO4)2

NASA Astrophysics Data System (ADS)

Ben Yahia, Hamdi; Essehli, Rachid; Amin, Ruhul; Boulahya, Khalid; Okumura, Toyoki; Belharouak, Ilias

2018-04-01

The compound NaFe2(PO4)(SO4)2 is successfully synthesized via a solid state reaction route and its crystal structure is determined using powder X-ray diffraction data. NaFe2(PO4)(SO4)2 phase is also characterized by cyclic voltammetry, galvanostatic cycling and electrochemical impedance spectroscopy. NaFe2(PO4)(SO4)2 crystallizes with the well-known NASICON-type structure. SAED and HRTEM experiments confirm the structural model, and no ordering between the PO4-3 and SO4-2 polyanions is detected. The electrochemical tests indicate that NaFe2(PO4)(SO4)2 is a 3 V sodium intercalating cathode. The electrical conductivity is relatively low (2.2 × 10-6 Scm-1 at 200 °C) and the obtained activation energy is ∼0.60eV. The GITT experiments indicate that the diffusivity values are in the range of 10-11-10-12 cm2/s within the measured sodium concentrations.

Hollow-cathode electrode for high-power, high-pressure discharge devices

DOEpatents

Chang, J.J.; Alger, T.W.

1995-08-22

Several different cold cathode configurations are disclosed for a gas discharge device each having a plurality of grooves of selected spacing, depth and width to improve the emission of electrons in a gas discharge device. Each of the cold cathode configurations can be machined from a single piece of a selected material. Several of the configurations can be assembled with individual elements which is easily seen from the various figures. 8 figs.

Battery Relevant Electrochemistry of Ag 7Fe 3(P 2O 7 ) 4 : Contrasting Contributions from the Redox Chemistries of Ag + and Fe 3+

DOE PAGES

Zhang, Yiman; Kirshenbaum, Kevin C.; Marschilok, Amy C.; ...

2016-10-12

Ag 7Fe 3(P 2O 7 ) 4 is an example of an electrochemical displacement material which contains two different electrochemically active metal cations, where one cation (Ag +) forms metallic silver nanoparticles external to the crystals of Ag 7Fe 3(P 2O 7 ) 4 via an electrochemical reduction displacement reaction, while the other cation (Fe +3) is electrochemically reduced with the retention of iron cations within the anion structural framework concomitant with lithium insertion. These contrasting redox chemistries within one pure cathode material enable high rate capability and reversibility when Ag 7Fe 3(P 2O 7 ) 4 is employed asmore » cathode material in a lithium ion battery (LIB). Further, pyrophosphate materials are thermally and electrically stable, desirable attributes for cathode materials in LIBs. In this article, a bimetallic pyrophosphate material Ag 7Fe 3(P 2O 7 ) 4 is synthesized and confirmed to be a single phase by Rietveld refinement. Electrochemistry of Ag 7Fe 3(P 2O 7 ) 4 is reported for the first time in the context of lithium based batteries using cyclic voltammetry and galvanostatic discharge–charge cycling. The reduction displacement reaction and the lithium (de)insertion processes are investigated using ex situ X-ray absorption spectroscopy and X-ray diffraction of electrochemically reduced and oxidized Ag 7Fe 3(P 2O 7 ) 4. Ag 7Fe 3(P 2O 7 ) 4 exhibits good reversibility at the iron centers indicated by ~80% capacity retention over 100 cycles following the initial formation cycle and excellent rate capability exhibited by ~70% capacity retention upon a 4-fold increase in current.« less

Battery Relevant Electrochemistry of Ag 7Fe 3(P 2O 7 ) 4 : Contrasting Contributions from the Redox Chemistries of Ag + and Fe 3+

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

Zhang, Yiman; Kirshenbaum, Kevin C.; Marschilok, Amy C.

Ag 7Fe 3(P 2O 7 ) 4 is an example of an electrochemical displacement material which contains two different electrochemically active metal cations, where one cation (Ag +) forms metallic silver nanoparticles external to the crystals of Ag 7Fe 3(P 2O 7 ) 4 via an electrochemical reduction displacement reaction, while the other cation (Fe +3) is electrochemically reduced with the retention of iron cations within the anion structural framework concomitant with lithium insertion. These contrasting redox chemistries within one pure cathode material enable high rate capability and reversibility when Ag 7Fe 3(P 2O 7 ) 4 is employed asmore » cathode material in a lithium ion battery (LIB). Further, pyrophosphate materials are thermally and electrically stable, desirable attributes for cathode materials in LIBs. In this article, a bimetallic pyrophosphate material Ag 7Fe 3(P 2O 7 ) 4 is synthesized and confirmed to be a single phase by Rietveld refinement. Electrochemistry of Ag 7Fe 3(P 2O 7 ) 4 is reported for the first time in the context of lithium based batteries using cyclic voltammetry and galvanostatic discharge–charge cycling. The reduction displacement reaction and the lithium (de)insertion processes are investigated using ex situ X-ray absorption spectroscopy and X-ray diffraction of electrochemically reduced and oxidized Ag 7Fe 3(P 2O 7 ) 4. Ag 7Fe 3(P 2O 7 ) 4 exhibits good reversibility at the iron centers indicated by ~80% capacity retention over 100 cycles following the initial formation cycle and excellent rate capability exhibited by ~70% capacity retention upon a 4-fold increase in current.« less

Layered P2-Na 2/3 Co 1/2 Ti 1/2 O 2 as a high-performance cathode material for sodium-ion batteries

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

Sabi, Noha; Doubaji, Siham; Hashimoto, Kazuki

Layered oxides are regarded as promising cathode materials for sodium-ion batteries. We present Na2/3Co1/2Ti1/2O2 as a potential new cathode material for sodium-ion batteries. The crystal features and morphology of the pristine powder were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The cathode material is evaluated in galvanostatic charge-discharge and galvanostatic intermittent titration tests, as well as ex-situ X-ray diffraction analysis. Synthesized by a high-temperature solid state reaction, Na2/3Co1/2Ti1/2O2 crystallizes in P2-type structure with P6(3)/mmc space group. The material presents reversible electrochemical behavior and delivers a specific discharge capacity of 100 mAh g(-1) when tested in Na halfmore » cells between 2.0 and 4.2 V (vs. Na+/Na), with capacity retention of 98% after 50 cycles. Furthermore, the electrochemical cycling of this titanium-containing material evidenced a reduction of the potential jumps recorded in the NaxCoO2 parent phase, revealing a positive impact of Ti substitution for Co. The ex-situ XRD measurements confirmed the reversibility and stability of the material. No structural changes were observed in the XRD patterns, and the P2-type structure was stable during the charge/discharge process between 2.0 and 4.2 V vs. Na+/Na. These outcomes will contribute to the progress of developing low cost electrode materials for sodium-ion batteries. (C) 2017 Elsevier B.V. All rights reserved.« less

Storage and Effective Migration of Li-Ion for Defected β-LiFePO 4 Phase Nanocrystals

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

Guo, Hua; Song, Xiaohe; Zhuo, Zengqing

2016-01-13

Lithium iron phosphate, a widely used cathode material, crystallizes typically in olivine-type phase, α-LiFePO4 (αLFP). However, the new phase β-LiFePO4 (βLFP), which can be transformed from αLFP under high temperature and pressure, is originally almost electrochemically inactive with no capacity for Li-ion battery, because the Li-ions are stored in the tetrahedral [LiO4] with very high activation barrier for migration and the one-dimensional (1D) migration channels for Li-ion diffusion in αLFP disappear, while the Fe ions in the β-phase are oriented similar to the 1D arrangement instead. In this work, using experimental studies combined with density functional theory calculations, we demonstratemore » that βLFP can be activated with creation of effective paths of Li-ion migration by optimized disordering. Thus, the new phase of βLFP cathode achieved a capacity of 128 mAh g–1 at a rate of 0.1 C (1C = 170 mA g–1) with extraordinary cycling performance that 94.5% of the initial capacity retains after 1000 cycles at 1 C. The activation mechanism can be attributed to that the induced disorder (such as FeLiLiFe antisite defects, crystal distortion, and amorphous domains) creates new lithium migration passages, which free the captive stored lithium atoms and facilitate their intercalation/deintercalation from the cathode. Such materials activated by disorder are promising candidate cathodes for lithium batteries, and the related mechanism of storage and effective migration of Li-ions also provides new clues for future design of disordered-electrode materials with high capacity and high energy density.« less

Storage and Effective Migration of Li-Ion for Defected β-LiFePO4 Phase Nanocrystals.

PubMed

Guo, Hua; Song, Xiaohe; Zhuo, Zengqing; Hu, Jiangtao; Liu, Tongchao; Duan, Yandong; Zheng, Jiaxin; Chen, Zonghai; Yang, Wanli; Amine, Khalil; Pan, Feng

2016-01-13

Lithium iron phosphate, a widely used cathode material, crystallizes typically in olivine-type phase, α-LiFePO4 (αLFP). However, the new phase β-LiFePO4 (βLFP), which can be transformed from αLFP under high temperature and pressure, is originally almost electrochemically inactive with no capacity for Li-ion battery, because the Li-ions are stored in the tetrahedral [LiO4] with very high activation barrier for migration and the one-dimensional (1D) migration channels for Li-ion diffusion in αLFP disappear, while the Fe ions in the β-phase are oriented similar to the 1D arrangement instead. In this work, using experimental studies combined with density functional theory calculations, we demonstrate that βLFP can be activated with creation of effective paths of Li-ion migration by optimized disordering. Thus, the new phase of βLFP cathode achieved a capacity of 128 mAh g(-1) at a rate of 0.1 C (1C = 170 mA g(-1)) with extraordinary cycling performance that 94.5% of the initial capacity retains after 1000 cycles at 1 C. The activation mechanism can be attributed to that the induced disorder (such as FeLiLiFe antisite defects, crystal distortion, and amorphous domains) creates new lithium migration passages, which free the captive stored lithium atoms and facilitate their intercalation/deintercalation from the cathode. Such materials activated by disorder are promising candidate cathodes for lithium batteries, and the related mechanism of storage and effective migration of Li-ions also provides new clues for future design of disordered-electrode materials with high capacity and high energy density.

Solid oxide fuel cell with single material for electrodes and interconnect

DOEpatents

McPheeters, Charles C.; Nelson, Paul A.; Dees, Dennis W.

1994-01-01

A solid oxide fuel cell having a plurality of individual cells. A solid oxide fuel cell has an anode and a cathode with electrolyte disposed therebetween, and the anode, cathode and interconnect elements are comprised of substantially one material.

Carbon-Supported Pd and PdFe Alloy Catalysts for Direct Methanol Fuel Cell Cathodes.

PubMed

Rivera Gavidia, Luis M; Sebastián, David; Pastor, Elena; Aricò, Antonino S; Baglio, Vincenzo

2017-05-25

Direct methanol fuel cells (DMFCs) are electrochemical devices that efficiently produce electricity and are characterized by a large flexibility for portable applications and high energy density. Methanol crossover is one of the main obstacles for DMFC commercialization, forcing the search for highly electro-active and methanol tolerant cathodes. In the present work, carbon-supported Pd and PdFe catalysts were synthesized using a sodium borohydride reduction method and physico-chemically characterized using transmission electron microscopy (TEM) and X-ray techniques such as photoelectron spectroscopy (XPS), diffraction (XRD) and energy dispersive spectroscopy (EDX). The catalysts were investigated as DMFC cathodes operating at different methanol concentrations (up to 10 M) and temperatures (60 °C and 90 °C). The cell based on PdFe/C cathode presented the best performance, achieving a maximum power density of 37.5 mW·cm -2 at 90 °C with 10 M methanol, higher than supported Pd and Pt commercial catalysts, demonstrating that Fe addition yields structural changes to Pd crystal lattice that reduce the crossover effects in DMFC operation.

Carbon-Supported Pd and PdFe Alloy Catalysts for Direct Methanol Fuel Cell Cathodes

PubMed Central

Rivera Gavidia, Luis M.; Sebastián, David; Pastor, Elena; Aricò, Antonino S.; Baglio, Vincenzo

2017-01-01

Direct methanol fuel cells (DMFCs) are electrochemical devices that efficiently produce electricity and are characterized by a large flexibility for portable applications and high energy density. Methanol crossover is one of the main obstacles for DMFC commercialization, forcing the search for highly electro-active and methanol tolerant cathodes. In the present work, carbon-supported Pd and PdFe catalysts were synthesized using a sodium borohydride reduction method and physico-chemically characterized using transmission electron microscopy (TEM) and X-ray techniques such as photoelectron spectroscopy (XPS), diffraction (XRD) and energy dispersive spectroscopy (EDX). The catalysts were investigated as DMFC cathodes operating at different methanol concentrations (up to 10 M) and temperatures (60 °C and 90 °C). The cell based on PdFe/C cathode presented the best performance, achieving a maximum power density of 37.5 mW·cm−2 at 90 °C with 10 M methanol, higher than supported Pd and Pt commercial catalysts, demonstrating that Fe addition yields structural changes to Pd crystal lattice that reduce the crossover effects in DMFC operation. PMID:28772937

Precipitation method for barium metaborate (BaB2O4) synthesis from borax solution

NASA Astrophysics Data System (ADS)

Akşener, Eymen; Figen, Aysel Kantürk; Pişkin, Sabriye

2013-12-01

In this study, barium metaborate (BaB2O4, BMB) synthesis from the borax solution was carried out. BMB currently is used in production of ceramic glazes, luminophors, oxide cathodes as well as additives to pigments for aqueous emulsion paints and also β-BaB2O4 single crystals are the best candidate for fabrication of solid-state UV lasers operating at a wavelength of 200 nm due to excellent nonlinear optical properties. In the present study, synthesis was carried out from the borax solution (Na2B4O7ṡ10H2O, BDH) and barium chloride (BaCI2ṡ2H2O, Ba) in the glass-batch reactor with stirring. The effect of, times (5-15 min), molar ratio [stoich.ration (1.0:2.0), 1.25:2.0, 1.5:2.0, 2.5:2:0, 3.0:2.0, 3.5:2.0,4.0:2.0, 5.0:2.0] and also crystallization time (2-6 hour) on the BMB yield (%) was investigated at 80 °C reaction temperature. It is found that, BMB precipitation synthesis with 90 % yield can be performed from 0.50 molar ration (BDH:Ba), under 80 °C, 15 minute, and 6 hours crystallization time. The structural properties of BMB powders were characterized by using XRD, FT-IR and DTA-TG instrumental analysis technique.

LiCaFeF6: A zero-strain cathode material for use in Li-ion batteries

NASA Astrophysics Data System (ADS)

de Biasi, Lea; Lieser, Georg; Dräger, Christoph; Indris, Sylvio; Rana, Jatinkumar; Schumacher, Gerhard; Mönig, Reiner; Ehrenberg, Helmut; Binder, Joachim R.; Geßwein, Holger

2017-09-01

A new zero-strain LiCaFeF6 cathode material for reversible insertion and extraction of lithium ions is presented. LiCaFeF6 is synthesized by a solid-state reaction and processed to a conductive electrode composite via high-energy ball-milling. In the first cycle, a discharge capacity of 112 mAh g-1 is achieved in the voltage range from 2.0 V to 4.5 V. The electrochemically active redox couple is Fe3+/Fe2+ as confirmed by Mössbauer spectroscopy and X-ray absorption spectroscopy. The compound has a trigonal colquiriite-type crystal structure (space group P 3 bar 1 c). By means of in situ and ex situ XRD as well as X-ray absorption fine structure spectroscopy a reversible response to Li uptake/release is found. For an uptake of 0.8 mol Li per formula unit only minimal changes occur in the lattice parameters causing a total change in unit cell volume of less than 0.5%. The spatial distribution of cations in the crystal structure as well as the linkage between their corresponding fluorine octahedra is responsible for this very small structural response. With its zero-strain behaviour this material is expected to exhibit only negligible mechanical degradation. It may be used as a cathode material in future lithium-ion batteries with strongly improved safety and cycle life.

Resolving the degradation pathways in high-voltage oxides for high-energy-density lithium-ion batteries; Alternation in chemistry, composition and crystal structures

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

Mohanty, Debasish; Mazumder, Baishakhi; Devaraj, Arun

Our development of stable high-voltage (HV), high capacity (HC) cathode oxides is indispensable to enhancing the performance of current high-energy-density (HED) lithium-ion batteries. Overstoichiometric, layered Li- and Mn-rich (LMR) composite oxides are promising materials for HV-HC cathodes for HED batteries; however, their practical use is limited. By probing the crystal structure, magnetic structure, and microstructure of the Li 1.2Mn 0.55Ni 0.15Co 0.1O 2 LMR oxide, we demonstrate that the oxide loses its pristine chemistry, structure, and composition during the first charge-discharge cycle and that it proceeds through a series of progressive events that introduce impediments on the ion mobility pathways.more » Here, we discovered i) the presence of tetrahedral Mn 3+, interlayer cation intermixing, interface of layered-spinel, and structurally rearranged domains, cation segregation at an HV charged state, and ii) the loss of Li ions, inhomogeneous distribution of Li/Ni, and structurally transformed domains after the first discharge. Our results will advance our fundamental understanding of the obstacles related to ion migration pathways in HV-HC cathode systems and will enable us to formulate design rules for use of such materials in high-energy-density electrochemical-energy-storage devices.« less

Resolving the degradation pathways in high-voltage oxides for high-energy-density lithium-ion batteries; Alternation in chemistry, composition and crystal structures

DOE PAGES

Mohanty, Debasish; Mazumder, Baishakhi; Devaraj, Arun; ...

2017-04-05

Our development of stable high-voltage (HV), high capacity (HC) cathode oxides is indispensable to enhancing the performance of current high-energy-density (HED) lithium-ion batteries. Overstoichiometric, layered Li- and Mn-rich (LMR) composite oxides are promising materials for HV-HC cathodes for HED batteries; however, their practical use is limited. By probing the crystal structure, magnetic structure, and microstructure of the Li 1.2Mn 0.55Ni 0.15Co 0.1O 2 LMR oxide, we demonstrate that the oxide loses its pristine chemistry, structure, and composition during the first charge-discharge cycle and that it proceeds through a series of progressive events that introduce impediments on the ion mobility pathways.more » Here, we discovered i) the presence of tetrahedral Mn 3+, interlayer cation intermixing, interface of layered-spinel, and structurally rearranged domains, cation segregation at an HV charged state, and ii) the loss of Li ions, inhomogeneous distribution of Li/Ni, and structurally transformed domains after the first discharge. Our results will advance our fundamental understanding of the obstacles related to ion migration pathways in HV-HC cathode systems and will enable us to formulate design rules for use of such materials in high-energy-density electrochemical-energy-storage devices.« less

Electrochemically influenced cation inter-diffusion and Co 3O 4 formation on La 0.6Sr 0.4CoO 3 infiltrated into SOFC cathodes

DOE PAGES

Song, Xueyan; Lee, Shiwoo; Chen, Yun; ...

2015-06-18

Nanosized LSC electrocatalyst was infiltrated into a porous scaffold cathode composed of Sm 2O 3-doped CeO 2 (SDC) and La 0.6Sr 0.4Co 0.2Fe 0.8O 3-δ (LSCF) in a commercial button solid oxide fuel cell (SOFC). To understand the stability of cathodes infiltrated with LSC, the infiltrated composite cells were subjected to both electrochemical operating and thermal aging states at 750 °C for 1500 h. Nanostructure and local chemistry evolution of La 0.6Sr 0.4CoO 3 (LSC) infiltrated cathodes upon operation and aging were investigated by transmission electron microscopy. After operation, the LSC remained a cubic perovskite, and the crystal grains exhibitmore » comparable size to as-infiltrated LSC grains. Inter-diffusion of Fe from the LSCF to a Fe-incorporated LSC layer developed on the LSCF backbone. However, only sharp interfaces were observed between LSC and SDC backbone in the as-infiltrated cathode and such interfaces remain after operation. The infiltrated LSC on the SDC backbone also retains granular particle morphology. Furthermore, newly grown Co 3O 4 nanocrystals were found in the operated cathode. After thermal aging, on the other hand, cation inter-diffusion across the interfaces of the infiltrate particles and the cathode backbones is less than that from the operated cells. Lastly, the following hypothesis is proposed: Co 3O 4 forms on LSC arising from local charge balancing between cobalt and oxygen vacancies.« less

Insertion of lattice strains into ordered LiNi0.5Mn1.5O4 spinel by mechanical stress: A comparison of perfect versus imperfect structures as a cathode for Li-ion batteries

NASA Astrophysics Data System (ADS)

Kozawa, Takahiro; Murakami, Takeshi; Naito, Makio

2016-07-01

The Ni-doped lithium manganese oxide, LiNi0.5Mn1.5O4, has received much attention as a cathode active material in high-energy lithium-ion batteries (LIBs). This active material has two different spinel structures depending on the ordering state of the Ni and Mn ions. The ordered LiNi0.5Mn1.5O4 spinel has an inferior cathode performance than the disordered phase because of its poor electronic conductivity. However, the ordered LiNi0.5Mn1.5O4 spinel possesses the potential advantage of avoiding dissolution of the Mn ion, which is an issue for the disordered spinel. The improvement of cathode performance is important for future applications. Here, we report a unique approach to improve the cathode performance of the ordered LiNi0.5Mn1.5O4 spinel. The mechanical treatment using an attrition-type mill successfully inserted lattice strains into the ordered LiNi0.5Mn1.5O4 spinel structure without a phase transformation to the disordered phase. The insertion of lattice strains by mechanical stresses provided an increased discharge capacity and a decreased charge transfer resistance. This limited crystal structure modification improved the cathode performance. The present work has the potential for application of the mechanically treated ordered LiNi0.5Mn1.5O4 spinel as a cathode for high-energy LIBs.

Facile design and synthesis of Li-rich nanoplates cathodes with habit-tuned crystal for lithium ion batteries

NASA Astrophysics Data System (ADS)

Li, Jili; Jia, Tiekun; Liu, Kai; Zhao, Junwei; Chen, Jian; Cao, Chuanbao

2016-11-01

Li-ion batteries with high-energy and high-power density are pursued to apply in the electronic vehicles and renewable energy storage systems. In this work, layered Li-rich transition-metal oxide cathode Li1.2Ni0.2Mn0.6O2 nanoplates with enhanced growth of {010} planes (LNMO-NP) is successfully synthesized through a facile and versatile strategy. Ethylene glycol plays an important role in the formation of LNMO-NP nanoplates with {010} electrochemically active surface planes exposure. As cathode for Li-ion batteries, LNMO-NP demonstrates a high specific discharge capacity of 270.2 mAh g-1 at 0.1 C (1 C = 300 mA g-1) and an excellent rate capability. The good electrochemical performance can be attributed to the nanoplates with the growth of {010} electrochemically active planes which is in favor of Li+ intercalation/deintercalation.

Collective acceleration of ions in picosecond pinched electron beams

NASA Astrophysics Data System (ADS)

Baryshnikov, V. I.; Paperny, V. L.; Shipayev, I. V.

2017-10-01

Сharacteristics of intense electron-ion beams emitted by a high-voltage (280 kV) electron accelerator with a pulse duration of 200 ps and current 5 kA are studied. The capture phenomena and the subsequent collective acceleration of multi charged ions of the cathode material by the electric field of the electron beam are observed. It is shown that the electron-ion beam diameter does not exceed 30 µm therein in the case of lighter ions, and the decay of the pinched beam occurs at a shorter distance from the cathode. It is established that the ions of the cathode material Tin+ captured by the electron beam are accelerated up to an energy of  ⩽10 MeV, and the ion fluence reaches 1017 ion cm-2 in the pulse. These ions are effectively embedded into the lattice sites of the irradiated substrate (sapphire crystal), forming the luminescent areas of the micron scale.

Abrasive-assisted Nickel Electroforming Process with Moving Cathode

NASA Astrophysics Data System (ADS)

REN, Jianhua; ZHU, Zengwei; XIA, Chunqiu; QU, Ningsong; ZHU, Di

2017-03-01

In traditional electroforming process for revolving parts with complex profiles, the drawbacks on surface of deposits, such as pinholes and nodules, will lead to varying physical and mechanical properties on different parts of electroformed components. To solve the problem, compositely moving cathode is employed in abrasive-assisted electroforming of revolving parts with complicated profiles. The cathode translates and rotates simultaneously to achieve uniform friction effect on deposits without drawbacks. The influences of current density and translation speed on the microstructure and properties of the electroformed nickel layers are investigated. It is found that abrasive-assisted electroforming with compound cathode motion can effectively remove the pinholes and nodules, positively affect the crystal nucleation, and refine the grains of layer. The increase of current density will lead to coarse microstructure and lower micro hardness, from 325 HV down to 189 HV. While, faster translational linear speed produces better surface quality and higher micro hardness, from 236 HV up to 283 HV. The weld-ability of the electroformed layers are also studied through the metallurgical analysis of welded joints between nickel layer and 304 stainless steel. The electrodeposited nickel layer shows fine performance in welding. The novel compound motion of cathode promotes the mechanical properties and refines the microstructure of deposited layer.

Gas block mechanism for water removal in fuel cells

DOEpatents

Issacci, Farrokh; Rehg, Timothy J.

2004-02-03

The present invention is directed to apparatus and method for cathode-side disposal of water in an electrochemical fuel cell. There is a cathode plate. Within a surface of the plate is a flow field comprised of interdigitated channels. During operation of the fuel cell, cathode gas flows by convection through a gas diffusion layer above the flow field. Positioned at points adjacent to the flow field are one or more porous gas block mediums that have pores sized such that water is sipped off to the outside of the flow field by capillary flow and cathode gas is blocked from flowing through the medium. On the other surface of the plate is a channel in fluid communication with each porous gas block mediums. The method for water disposal in a fuel cell comprises installing the cathode plate assemblies at the cathode sides of the stack of fuel cells and manifolding the single water channel of each of the cathode plate assemblies to the coolant flow that feeds coolant plates in the stack.

Note: design and development of improved indirectly heated cathode based strip electron gun.

PubMed

Maiti, Namita; Bade, Abhijeet; Tembhare, G U; Patil, D S; Dasgupta, K

2015-02-01

An improved design of indirectly heated solid cathode based electron gun (200 kW, 45 kV, 270° bent strip type electron gun) has been presented. The solid cathode is made of thoriated tungsten, which acts as an improved source of electron at lower temperature. So, high power operation is possible without affecting structural integrity of the electron gun. The design issues are addressed based on the uniformity of temperature on the solid cathode and the single long filament based design. The design approach consists of simulation followed by extensive experimentation. In the design, the effort has been put to tailor the non-uniformity of the heat flux from the filament to the solid cathode to obtain better uniformity of temperature on the solid cathode. Trial beam experiments have been carried out and it is seen that the modified design achieves one to one correspondence of the solid cathode length and the electron beam length.

Note: Design and development of improved indirectly heated cathode based strip electron gun

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

Maiti, Namita; Patil, D. S.; Dasgupta, K.

An improved design of indirectly heated solid cathode based electron gun (200 kW, 45 kV, 270° bent strip type electron gun) has been presented. The solid cathode is made of thoriated tungsten, which acts as an improved source of electron at lower temperature. So, high power operation is possible without affecting structural integrity of the electron gun. The design issues are addressed based on the uniformity of temperature on the solid cathode and the single long filament based design. The design approach consists of simulation followed by extensive experimentation. In the design, the effort has been put to tailor themore » non-uniformity of the heat flux from the filament to the solid cathode to obtain better uniformity of temperature on the solid cathode. Trial beam experiments have been carried out and it is seen that the modified design achieves one to one correspondence of the solid cathode length and the electron beam length.« less

POWER AND THERMAL TECHNOLOGIES FOR AIR AND SPACE-SCIENTIFIC RESEARCH PROGRAM Delivery Order 0018: Single Ion Conducting Solid-State Lithium Electrochemical Technologies (Task 4)

DTIC Science & Technology

2010-08-01

a mathematical equation relates the cathode reaction reversible electric potential to the lithium content of the cathode electrode. Based on the...Transport of Lithium in the Cell Cathode Active Material The Nernst -Einstein relation linking the lithium-ion mass diffusivity and its ionic...transient, isothermal and isobaric conditions. The differential model equation describing the lithium diffusion and accumulation in a spherical, active

Effects of hydraulic pressure on the performance of single chamber air-cathode microbial fuel cells.

PubMed

Cheng, Shaoan; Liu, Weifeng; Guo, Jian; Sun, Dan; Pan, Bin; Ye, Yaoli; Ding, Weijun; Huang, Haobin; Li, Fujian

2014-06-15

Scaling up of microbial fuel cells (MFCs) without losing power density requires a thorough understanding of the effect of hydraulic pressure on MFC performance. In this work, the performance of an activated carbon air-cathode MFC was evaluated under different hydraulic pressures. The MFC under 100 mmH2O hydraulic pressure produced a maximum power density of 1260 ± 24 mW m(-2), while the power density decreased by 24.4% and 44.7% as the hydraulic pressure increased to 500 mmH2O and 2000 mmH2O, respectively. Notably, the performance of both the anode and the cathode had decreased under high hydraulic pressures. Electrochemical impedance spectroscopy tests of the cathode indicated that both charge transfer resistance and diffusion transfer resistance increased with the increase in hydraulic pressure. Denaturing gradient gel electrophoresis of PCR-amplified partial 16S rRNA genes demonstrated that the similarity among anodic biofilm communities under different hydraulic pressures was ≥ 90%, and the communities of all MFCs were dominated by Geobacter sp. These results suggested that the reduction in power output of the single chamber air-cathode MFC under high hydraulic pressures can be attributed to water flooding of the cathode and suppression the metabolism of anodic exoelectrogenic bacteria. Copyright © 2014 Elsevier B.V. All rights reserved.

Two-photon photoemission from a copper cathode in an Χ-band photoinjector

DOE PAGES

Li, H.; Limborg-Deprey, C.; Adolphsen, C.; ...

2016-02-24

This study presents two-photon photoemission from a copper cathode in an X-band photoinjector. We experimentally verified that the electron bunch charge from photoemission out of a copper cathode scales with laser intensity (I) square for 400 nm wavelength photons. We compare this two-photon photoemission process with the single photon process at 266 nm. Despite the high reflectivity (R) of the copper surface for 400 nm photons (R=0.48) and higher thermal energy of photoelectrons (two-photon at 200 nm) compared to 266 nm photoelectrons, the quantum efficiency of the two-photon photoemission process (400 nm) exceeds the single-photon process (266 nm) when themore » incident laser intensity is above 300 GW/cm 2. At the same laser pulse energy (E) and other experimental conditions, emitted charge scales inversely with the laser pulse duration. A thermal emittance of 2.7 mm-mrad per mm root mean square (rms) was measured on our cathode which exceeds by sixty percent larger compared to the theoretical predictions, but this discrepancy is similar to previous experimental thermal emittance on copper cathodes with 266 nm photons. The damage of the cathode surface of our first-generation X-band gun from both rf breakdowns and laser impacts mostly explains this result. Using a 400 nm laser can substantially simplify the photoinjector system, and make it an alternative solution for compact pulsed electron sources.« less

Modification of polymer velvet cathode via metallic Mo coating for enhancement of high-current electron emission performances

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

Xiong, Ying; Wang, Bing; Yi, Yong

2013-09-15

The effect of surface Mo coating on the high-current electron emission performances for polymer velvet cathode has been investigated in a diode with A-K gap of 11.5 cm by the combination of time-resolved electrical diagnostic and temporal pressure variation. Compared with uncoated polymer velvet cathode under the single-pulsed emission mode, the Mo-coated one shows lower outgassing levels (∼0.40 Pa L), slower cathode plasma expansion velocity (∼2.30 cm/μs), and higher emission stability as evidences by the change in cathode current, temporal pressure variation, and diode perveance. Moreover, after Mo coating, the emission consistency of the polymer velvet cathode between two adjacentmore » pulses is significantly improved in double-pulsed emission mode with ∼500 ns interval between two pulses, which further confirms the effectiveness of Mo coating for enhancement of electron emission performance of polymer velvet cathodes. These results should be of interest to the high-repetitive high-power microwave systems with cold cathodes.« less

The first naphthosemiquinone complex of K+ with vitamin K3 analog: Experiment and density functional theory

NASA Astrophysics Data System (ADS)

Kathawate, Laxmi; Gejji, Shridhar P.; Yeole, Sachin D.; Verma, Prakash L.; Puranik, Vedavati G.; Salunke-Gawali, Sunita

2015-05-01

Synthesis and characterization of potassium complex of 2-hydroxy-3-methyl-1,4-naphthoquinone (phthiocol), the vitamin K3 analog, has been carried out using FT-IR, UV-Vis, 1H and 13C NMR, EPR, cyclic voltammetry and single crystal X-ray diffraction experiments combined with the density functional theory. It has been observed that naphthosemiquinone binds to two K+ ions extending the polymeric chain through bridging oxygens O(2) and O(3). The crystal network possesses hydrogen bonding interactions from coordinated water molecules showing water channels along the c-axis. 13C NMR spectra revealed that the complexation of phthiocol with potassium ion engenders deshielding of C(2) signals, which appear at δ = ∼14.6 ppm whereas those of C(3) exhibit up-field signals near δ ∼ 6.9 ppm. These inferences are supported by the M06-2x based density functional theory. Electrochemical experiments further suggest that reduction of naphthosemiquinone results in only a cathodic peak from catechol. A triplet state arising from interactions between neighboring phthiocol anion lead to a half field signal at g = 4.1 in the polycrystalline X-band EPR spectra at 133 K.

Pulsed electromagnetic gas acceleration. [magnetohydrodynamics, plasma power sources and plasma propulsion

NASA Technical Reports Server (NTRS)

Jahn, R. G.; Vonjaskowsky, W. F.; Clark, K. E.

1975-01-01

Terminal voltage measurements with various cathodes and anodes in a high power, quasi-steady magnetoplasmadynamic (MPD) are discussed. The magnitude of the current at the onset of voltage fluctuations is shown to be an increasing function of cathode area and a weaker decreasing function of anode area. Tests with a fluted cathode indicated that the fluctuations originate in the plasma adjacent to the cathode rather than at the cathode surface. Measurements of radiative output from an optical cavity aligned to examine the current-carrying portion of a two-dimensional, 56 kA magnetoplasmadynamic discharge reveal no lasing in that region, consistent with calculations of electron excitation and resonance radiation trapping. A voltage-swept double probe technique allows single-shot determination of electron temperature and electron number density in the recombining MPD exhaust flow. Current distributions within the cavity of MPD hollow cathodes for various static prefills with no injected mass flow are examined.

Transport phenomena in polymer electrolyte membrane fuel cells via voltage loss breakdown

NASA Astrophysics Data System (ADS)

Flick, Sarah; Dhanushkodi, Shankar R.; Mérida, Walter

2015-04-01

This study presents a voltage loss breakdown method based on in-situ experimental data to systematically analyze the different overpotentials of a polymer electrolyte membrane fuel cell. This study includes a systematic breakdown of the anodic overpotentials via the use of a reference electrode system. This work demonstrates the de-convolution of the individual overpotentials for both anode and cathode side, including the distinction between mass-transport overpotentials in cathode porous transport layer (PTL) and electrode, based on in-situ polarization tests under different operating conditions. This method is used to study the relationship between mass-transport losses inside the cathode catalyst layer (CL) and the PTL for both a single layer and two-layer PTL configuration. We conclude that the micro-porous layer (MPL) significantly improves the water removal within the cell, especially inside the cathode electrode, and therefore the mass transport within the cathode CL. This study supports the theory that the MPL on the cathode leads to an increase in water permeation from cathode to anode due to its function as a capillary barrier. This is reflected in increased anodic mass-transport overpotential, decreased ohmic losses and decreased cathode mass-transport losses, especially in the cathode electrode.

Solid oxide fuel cell with single material for electrodes and interconnect

DOEpatents

McPheeters, C.C.; Nelson, P.A.; Dees, D.W.

1994-07-19

A solid oxide fuel cell is described having a plurality of individual cells. A solid oxide fuel cell has an anode and a cathode with electrolyte disposed there between, and the anode, cathode and interconnect elements are comprised of substantially one material. 9 figs.

Metal Photocathodes for Free Electron Laser Applications

NASA Astrophysics Data System (ADS)

Greaves, Corin Michael Ricardo

Synchrotron x-ray radiation sources have revolutionized many areas of science from elucidating the atomic structure of proteins to understanding the electronic structure of complex materials such as the cuprate superconductors. In a Free Electron Laser (FEL), the main difference to the synchrotron radiation mechanism is that the light field acts on the electron beam, over a long distance in an undulator, and causes electron bunching at the optical wavelength. Electrons in different parts of the electron bunch are therefore correlated, and so emit coherently, with a brightness that scales as the square of the number of electrons. In order to lase, the electron beam in a FEL must have a transverse geometric emittance less than the wavelength of the light to be produced. For the generation of x-ray wavelengths, this is one of the most difficult challenges in the design and construction of a FEL. The geometric emittance can be "compressed" by acceleration to very high energy, but with the penalty of very large physical size and very large cost. The motivation for this work was provided by the desire to investigate the fundamental origin of the emittance of an electron beam as it is born at a photocathode. If this initial, or "thermal" emittance can be reduced, the energy, scale and cost of accelerators potentially would be reduced. As the LCLS used copper as its photocathode, this material was the one studied in this work. Copper was used in the LCLS as it represented a "robust" material that could stand the very high accelerating gradients used in the photoinjector of the FEL. Metals are also prompt photoemitters, and so can be used to produce very short electron bunches. This can be a useful property for creation of extremely short FEL pulses, and also for creation of beams that are allowed to expand under space charge forces, but in a way that results in linear fields, allowing subsequent recompression. An ideal photocathode for FEL photoinjector should have high quantum efficiency (QE), small emittance, fast temporal response, long lifetime, and minimal complexity. High QE of cathodes require less power for driving laser and also reduce the risk of damaging the cathode materials. Small emittance reduce the scale of the accelerator, therefore, the cost. Metal photocathodes such as copper exhibit long lifetime and fast response, but have quite low quantum efficiency ( < 10-4). The aim in this work was to understand the quantum yield of the metal, and the transverse momentum spectrum, as the product of the latter and the cathode beam spot size gives the transverse emittance. Initial x-ray diffraction work provided evidence that the LCLS photocathode consisted of large low index single crystal grains, and so work focused on the study of single crystals that could be produced with atomically ordered surfaces, rather than a polycrystalline material. Present theories of quantum yield and transverse emittance assume the basic premise that the metal is entirely disordered, and work here shows that this is fundamentally incorrect, and that the order of the surface plays a critical role in determining the characteristics of emission. In order to investigate these surfaces, I constructed a laser-based ultra-low energy angle resolved photoemission system, capable of measuring the momentum spectrum of the emission and wavelength and angle dependent electron yield. This system has been commissioned, and data taken on low index surfaces of copper. Results from this work on single crystal copper demonstrates that emitted electrons from the band structure of a material can exhibit small emittance and high quantum efficiency. We show that the emission from the Cu(111) surface state is highly correlated between angle of incidence and excitation energy. This manifests itself in the form of a truncated emission cone, rather than the isotropic emission predicted from the normal model. This clearly then reduces the emittance from the normal values. It also results in extremely strong polarization dependence, with p-s asymmetry of up to 16 at low photon energy. It also directly suggests ways through changing materials, or by material design to significantly reduce emittance, at the same time increasing electron yield. These results show the benefits that could be gained from electronic engineering of cathodes and should have direct impact in the design of future FEL photoinjectors. (Abstract shortened by UMI.)

Solid oxide membrane (SOM) process for ytterbium and silicon production from their oxides

NASA Astrophysics Data System (ADS)

Jiang, Yihong

The Solid oxide membrane (SOM) electrolysis is an innovative green technology that produces technologically important metals directly from their respective oxides. A yttria-stabilized zirconia (YSZ) tube, closed at one end is employed to separate the molten salt containing dissolved metal oxides from the anode inside the YSZ tube. When the applied electric potential between the cathode in the molten salt and the anode exceeds the dissociation potential of the desired metal oxides, oxygen ions in the molten salt migrate through the YSZ membrane and are oxidized at the anode while the dissolved metal cations in the flux are reduced to the desired metal at the cathode. Compared with existing metal production processes, the SOM process has many advantages such as one unit operation, less energy consumption, lower capital costs and zero carbon emission. Successful implementation of the SOM electrolysis process would provide a way to mitigate the negative environmental impact of the metal industry. Successful demonstration of producing ytterbium (Yb) and silicon (Si) directly from their respective oxides utilizing the SOM electrolysis process is presented in this dissertation. During the SOM electrolysis process, Yb2O3 was reduced to Yb metal on an inert cathode. The melting point of the supporting electrolyte (LiF-YbF3-Yb2O3) was determined by differential thermal analysis (DTA). Static stability testing confirmed that the YSZ tube was stable with the flux at operating temperature. Yb metal deposit on the cathode was confirmed by scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS). During the SOM electrolysis process for silicon production, a fluoride based flux based on BaF2, MgF2, and YF3 was engineered to serve as the liquid electrolyte for dissolving silicon dioxide. YSZ tube was used to separate the molten salt from an anode current collector in the liquid silver. Liquid tin was chosen as cathode to dissolve the reduced silicon during SOM electrolysis. After electrolysis, upon cooling, silicon crystals precipitated out from the Si-Sn liquid alloy. The presence of high-purity silicon crystals in the liquid tin cathode was confirmed by SEM/EDS. The fluoride based flux was also optimized to improve YSZ membrane stability for long-term use.

X-ray Diffraction Studies of the Structure and Thermochemistry of Alkaline-Earth Oxide-Coated Thermionic Cathodes

NASA Technical Reports Server (NTRS)

Karikari, E. K.; Bassey, E.; Wintucky, Edwin G.

1998-01-01

NASA LeRC has a broad, active cathode technology development program in which both experimental and theoretical studies are being employed to further development of thermionic cathodes for use as electron sources in vacuum devices for communications and other space applications. One important type of thermionic cathode under development is the alkaline-earth oxide-coated (BaO, SrO, CaO) cathode. Significant improvements in the emission characteristics of this cathode have been obtained through modification of the chemical composition and morphology of the oxide coating, with the best result thus far coming from the addition of In2O3 and Sc2O3. Whereas the In2O3 produces a finer, more uniform particle structure, the exact chemical state and role of the Sc2O3 in the emission enhancement is unknown. The purpose of this cooperative agreement is to combine the studies of the surface chemistry and electron emission at NASA LeRC of chemically modified oxide coatings with a study of the thermochemistry and crystal structure using X-ray diffraction equipment and expertise at Clark Atlanta University (CAU). The study at CAU is intended to provide the description and understanding of the structure and thermochemistry needed for further improvement and optimization of the modified coatings. A description of the experimental procedure, preliminary X-ray diffraction test results, together with the design of an ultrahigh vacuum chamber necessary for high temperature thermochemistry studies will be presented.

Cathodic Deposition of Mg(OH)2 Coatings on Pure mg in Three mg Salts Aqueous Solutions

NASA Astrophysics Data System (ADS)

Yongjun, Zhang; Xiaomeng, Pei; Shugong, Jia

Film-forming effects of cathodic deposition on pure Mg substrate at constant DC in aqueous solutions of magnesium nitrate (Mg(NO3)2ṡ6H2O), magnesium chloride (MgCl2ṡ6H2O) and magnesium sulfate (MgSO4ṡ7H2O) respectively were investigated systematically. Typical processes were studied by potentiodynamic cathodic polarization and galvanostatic polarization and typical samples were analyzed by SEM and XRD. The results indicate that the depositing efficiency is not only the highest but stablest, and deposited coatings show the best uniformity with Mg(NO3)2ṡ6H2O solution employed as depositing medium and applied current density ≥1.0mA cm-2. Cathodic deposition leads to regular mass loss of Mg substrate. The cathodic polarization curve of pure Mg in magnesium nitrate solution shows more obvious pseudo-passivation, several Tafel regions with different slopes appearing before diffusion-limited current density region, and oxygen consumption is the major cathodic reduction reaction under specified current density. However, hydrogen evolution reaction is dominant in both Mg chloride and Mg sulfate solutions. The deposition coatings are all composed of continuous and uniform mesh-like “basic layer” adjacent to substrate and discrete distributed snowball-like particles on the microscopic scale. The phase compositions are all crystal Mg(OH)2, and the coatings deposited in Mg chloride solution have (011) preferred orientation.

An electromagnetic/electrostatic dual cathode system for electron beam instruments

NASA Technical Reports Server (NTRS)

Bradley, J. G.; Conley, J. M.; Wittry, D. B.; Albee, A. L.

1986-01-01

A method of providing cathode redundancy which consists of two fixed cathodes and uses electromagnetic and/or electrostatic fields to direct the electron beam to the electron optical axis is presented, with application to the cathode system of the Scanning Electron Microscope and Particle Analyzer proposed for NASA's Mariner Mark II Comet Rendezvous/Asteroid Flyby projected for the 1990s. The symmetric double deflection system chosen has the optical property that the image of the effective electron source is formed above the magnet assembly near the apparent position of the effective source, and it makes the transverse positions of the electron sources independent of the electron beam energy. Good performance of the system is found, with the sample imaging resolution being the same as for the single-axis cathode.

Multi-angle nuclear imaging apparatus and method

DOEpatents

Anger, Hal O. [Berkeley, CA

1980-04-08

Nuclear imaging apparatus for obtaining multi-plane readouts of radioactive material in a human or animal subject. A probe disposed in the vicinity of the subject is provided for receiving radiation from radiating sources in the subject and for forming a probe radiation image. The probe has a collimator with different portions thereof having holes disposed at different angles. A single scintillation crystal overlies the collimator for receiving radiation passing through the collimator and producing scintillations to provide the probe image. An array of photomultiplier tubes overlie the single crystal for observing the probe image and providing electrical outputs. Conversion apparatus is provided for converting the electrical outputs representing the probe image into optical images displayed on the screen of a cathode ray tube. Divider apparatus is provided for dividing the probe radiation image into a plurality of areas with the areas corresponding to different portions of the collimator having holes disposed at different angles. A light sensitive medium is provided for receiving optical images. Apparatus is provided for causing relative movement between the probe and the subject. Apparatus is also provided for causing relative movement between the optical image on the screen and the light sensitive medium which corresponds to the relative movement between the probe and the subject whereby there is produced on the light sensitive medium a plurality of images that portray the subject as seen from different angles corresponding to the portions of the collimator having holes at different angles.

Multi-angle nuclear imaging apparatus and method

DOEpatents

Anger, H.O.

1980-04-08

A nuclear imaging apparatus is described for obtaining multi-plane readouts of radioactive material in a human or animal subject. A probe disposed in the vicinity of the subject is provided for receiving radiation from radiating sources in the subject and for forming a probe radiation image. The probe has a collimator with different portions having holes disposed at different angles. A single scintillation crystal overlies the collimator for receiving radiation passing through the collimator and producing scintillations to provide the probe image. An array of photomultiplier tubes overlie the single crystal for observing the probe image and providing electrical outputs. Conversion apparatus is provided for converting the electrical outputs representing the probe image into optical images displayed on the screen of a cathode ray tube. Divider apparatus is provided for dividing the probe radiation image into a plurality of areas with the areas corresponding to different portions of the collimator having holes disposed at different angles. A light sensitive medium is provided for receiving optical images. Apparatus is provided for causing relative movement between the probe and the subject. Apparatus is also provided for causing relative movement between the optical image on the screen and the light sensitive medium which corresponds to the relative movement between the probe and the subject whereby there is produced on the light sensitive medium a plurality of images that portray the subject as seen from different angles corresponding to the portions of the collimator having holes at different angles. 11 figs.

Structure-electrochemical evolution of a Mn-rich P2 Na 2/3Fe 0.2Mn 0.8O 2 Na-ion battery cathode

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

Dose, Wesley M.; Sharma, Neeraj; Pramudita, James C.

The structural evolution of electrode materials directly influences the performance of sodium-ion batteries. In this work, in situ synchrotron X-ray diffraction is used to investigate the evolution of the crystal structure of a Mn-rich P2-phase Na 2/3Fe 0.2Mn 0.8O 2 cathode. A single-phase reaction takes place for the majority of the discharge–charge cycle at ~C/10, with only a short, subtle hexagonal P2 to hexagonal P2 two-phase region early in the first charge. Thus, a higher fraction of Mn compared to previous studies is demonstrated to stabilize the P2 structure at high and low potentials, with neither “Z”/OP4 phases in themore » charged state nor significant quantities of the P'2 phase in the discharged state between 1.5 and 4.2 V. Notably, sodium ions inserted during discharge are located on both available crystallographic sites, albeit with a preference for the site sharing edges with the MO 6 octahedral unit. The composition Na ~0.70Fe 0.2Mn 0.8O 2 prompts a reversible single-phase sodium redistribution between the two sites. Sodium ions vacate the site sharing faces (Naf), favoring the site sharing edges (Nae) to give a Nae/Naf site occupation of 4:1 in the discharged state. This site preference could be an intermediate state prior to the formation of the P'2 phase. Furthermore, this work shows how the Mn-rich Na 2/3Fe 0.2Mn 0.8O 2 composition and its sodium-ion distribution can minimize phase transitions during battery function, especially in the discharged state.« less

Structure-electrochemical evolution of a Mn-rich P2 Na 2/3Fe 0.2Mn 0.8O 2 Na-ion battery cathode

DOE PAGES

Dose, Wesley M.; Sharma, Neeraj; Pramudita, James C.; ...

2017-08-04

The structural evolution of electrode materials directly influences the performance of sodium-ion batteries. In this work, in situ synchrotron X-ray diffraction is used to investigate the evolution of the crystal structure of a Mn-rich P2-phase Na 2/3Fe 0.2Mn 0.8O 2 cathode. A single-phase reaction takes place for the majority of the discharge–charge cycle at ~C/10, with only a short, subtle hexagonal P2 to hexagonal P2 two-phase region early in the first charge. Thus, a higher fraction of Mn compared to previous studies is demonstrated to stabilize the P2 structure at high and low potentials, with neither “Z”/OP4 phases in themore » charged state nor significant quantities of the P'2 phase in the discharged state between 1.5 and 4.2 V. Notably, sodium ions inserted during discharge are located on both available crystallographic sites, albeit with a preference for the site sharing edges with the MO 6 octahedral unit. The composition Na ~0.70Fe 0.2Mn 0.8O 2 prompts a reversible single-phase sodium redistribution between the two sites. Sodium ions vacate the site sharing faces (Naf), favoring the site sharing edges (Nae) to give a Nae/Naf site occupation of 4:1 in the discharged state. This site preference could be an intermediate state prior to the formation of the P'2 phase. Furthermore, this work shows how the Mn-rich Na 2/3Fe 0.2Mn 0.8O 2 composition and its sodium-ion distribution can minimize phase transitions during battery function, especially in the discharged state.« less

Crystal Chemistry and Electrochemistry of Li xMn 1.5Ni 0.5O 4 Solid Solution Cathode Materials

DOE PAGES

Kan, Wang Hay; Kuppan, Saravanan; Cheng, Lei; ...

2017-07-19

For ordered high-voltage spinel LiMn 1.5Ni 0.5O 4 (LMNO) with the P4 32 1 symmetry, the two consecutive two-phase transformations at ~4.7 V (vs Li +/Li), involving three cubic phases of LMNO, Li 0.5Mn 1.5Ni 0.5O 4 (L 0.5MNO), and Mn 1.5Ni 0.5O 4 (MNO), have been well-established. Such a mechanism is traditionally associated with poor kinetics due to the slow movement of the phase boundaries and the large mechanical strain resulting from the volume changes among the phases, yet ordered LMNO has been shown to have excellent rate capability. In this paper, we show the ability of the phasesmore » to dissolve into each other and determine their solubility limit. We characterized the properties of the formed solid solutions and investigated the role of non-equilibrium single-phase redox processes during the charge and discharge of LMNO. Finally, by using an array of advanced analytical techniques, such as soft and hard X-ray spectroscopy, transmission X-ray microscopy, and neutron/X-ray diffraction, as well as bond valence sum analysis, the present study examines the metastable nature of solid-solution phases and provides new insights in enabling cathode materials that are thermodynamically unstable.« less

Correlation Between Microstructure and Optical Properties of Cu (In0.7, Ga0.3) Se2 Grown by Electrodeposition Technique

NASA Astrophysics Data System (ADS)

Chihi, Adel; Bessais, Brahim

2017-01-01

Polycrystalline thin films Cu (In0.7, Ga0.3) Se2 (CIGSe) were grown on copper foils at various cathodic potentials by using an electrodeposition technique. Scanning electron microscopy showed that the average diameter of CIGSe grains increase from 0.1 μm to 1 μm when the cathodic potential decreases. The structure and surface morphology were investigated by x-ray diffraction and atomic force microscopy (AFM) techniques. This structure study shows that the thin films were well crystallized in a chalcopyrite structure without unwanted secondary phases with a preferred orientation along (112) plane. Energy-dispersive x-ray analyses confirms the existence of CIGSe single phase on a copper substrate. AFM analysis indicated that the root mean square roughness decreases from 64.28 to 27.42 when the potential deposition increases from -0.95 V to -0.77 V. Using Raman scattering spectroscopy, the A1 optical phonon mode was observed in 173 cm-1 and two other weak peaks were detected at 214 cm-1 and 225 cm-1 associated with the B2 and E modes of the CIGSe phase. Through spectroscopy ellipsometry analysis, a three-layer optical model was exploited to derive the optical properties and layer thickness of the CIGSe film by least-squares fitting the measured variation in polarization light versus the obtained microstructure.

Theory and simulation of backbombardment in single-cell thermionic-cathode electron guns

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

Edelen, J.  P.; Biedron, S.  G.; Harris, J.  R.

This paper presents a comparison between simulation results and a first principles analytical model of electron back-bombardment developed at Colorado State University for single-cell, thermionic-cathode rf guns. While most previous work on back-bombardment has been specific to particular accelerator systems, this work is generalized to a wide variety of guns within the applicable parameter space. The merits and limits of the analytic model will be discussed. This paper identifies the three fundamental parameters that drive the back-bombardment process, and demonstrates relative accuracy in calculating the predicted back-bombardment power of a single-cell thermionic gun.

Theory and simulation of backbombardment in single-cell thermionic-cathode electron guns

DOE PAGES

Edelen, J.  P.; Biedron, S.  G.; Harris, J.  R.; ...

2015-04-01

This paper presents a comparison between simulation results and a first principles analytical model of electron back-bombardment developed at Colorado State University for single-cell, thermionic-cathode rf guns. While most previous work on back-bombardment has been specific to particular accelerator systems, this work is generalized to a wide variety of guns within the applicable parameter space. The merits and limits of the analytic model will be discussed. This paper identifies the three fundamental parameters that drive the back-bombardment process, and demonstrates relative accuracy in calculating the predicted back-bombardment power of a single-cell thermionic gun.

Enigmatic Moisture Effects on Al2O3 Scale and TBC Adhesion

NASA Technical Reports Server (NTRS)

Smialek, James L.

2008-01-01

Alumina scale adhesion to high temperature alloys is known to be affected primarily by sulfur segregation and reactive element additions. However, adherent scales can become partially compromised by excessive strain energy and cyclic cracking. With time, exposure of such scales to moisture can lead to spontaneous interfacial decohesion, occurring while the samples are maintained at ambient conditions. Examples of this Moisture-Induced Delayed Spallation (MIDS) are presented for NiCrAl and single crystal superalloys, becoming more severe with sulfur level and cyclic exposure conditions. Similarly, delayed failure or Desk Top Spallation (DTS) results are reviewed for thermal barrier coatings (TBCs), culminating in the water drop failure test. Both phenomena are discussed in terms of moisture effects on bulk alumina and bulk aluminides. A mechanism is proposed based on hydrogen embrittlement and is supported by a cathodic hydrogen charging experiment. Hydroxylation of aluminum from the alloy interface appears to be the relevant basic reaction.

Enigmatic Moisture Effects on Al2O3 Scale and TBC Adhesion

NASA Technical Reports Server (NTRS)

Smialek, James L.

2008-01-01

Alumina scale adhesion to high temperature alloys is known to be affected primarily by sulfur segregation and reactive element additions. However adherent scales can become partially compromised by excessive strain energy and cyclic cracking. With time, exposure of such scales to moisture can lead to spontaneous interfacial decohesion, occurring while the samples are maintained at ambient conditions. Examples of this Moisture-Induced Delayed Spallation (MIDS) are presented for NiCrAl and single crystal superalloys, becoming more severe with sulfur level and cyclic exposure conditions. Similarly, delayed failure or Desk Top Spallation (DTS) results are reviewed for TBC s, culminating in the water drop failure test. Both phenomena are discussed in terms of moisture effects on bulk alumina and bulk aluminides. A mechanism is proposed based on hydrogen embrittlement and is supported by a cathodic hydrogen charging experiment. Hydroxylation of aluminum from the alloy interface appears to be the relevant basic reaction.

Electron beam emission from a diamond-amplifier cathode.

PubMed

Chang, Xiangyun; Wu, Qiong; Ben-Zvi, Ilan; Burrill, Andrew; Kewisch, Jorg; Rao, Triveni; Smedley, John; Wang, Erdong; Muller, Erik M; Busby, Richard; Dimitrov, Dimitre

2010-10-15

The diamond amplifier (DA) is a new device for generating high-current, high-brightness electron beams. Our transmission-mode tests show that, with single-crystal, high-purity diamonds, the peak current density is greater than 400  mA/mm², while its average density can be more than 100  mA/mm². The gain of the primary electrons easily exceeds 200, and is independent of their density within the practical range of DA applications. We observed the electron emission. The maximum emission gain measured was 40, and the bunch charge was 50  pC/0.5  mm². There was a 35% probability of the emission of an electron from the hydrogenated surface in our tests. We identified a mechanism of slow charging of the diamond due to thermal ionization of surface states that cancels the applied field within it. We also demonstrated that a hydrogenated diamond is extremely robust.

Field emission and photoluminescence characteristics of ZnS nanowires via vapor phase growth

NASA Astrophysics Data System (ADS)

Chang, Yongqin; Wang, Mingwei; Chen, Xihong; Ni, Saili; Qiang, Weijing

2007-05-01

Large-area ZnS nanowires were synthesized through a vapor phase deposition method. X-ray diffraction and electron microscopy results show that the products are composed of single crystalline ZnS nanowires with a cubic structure. The nanowires have sharp tips and are distributed uniformly on silicon substrates. The diameter of the bases is in the range of 320-530 nm and that of the tips is around 20-30 nm. The strong ultraviolet emission in the photoluminescence spectra also demonstrates that the ZnS nanowires are of high crystalline perfection. Field emission measurements reveal that the ZnS nanowires have a fairly low threshold field, which may be ascribed to their very sharp tips, rough surfaces and high crystal quality. The perfect field emission ability of the ZnS nanowires makes them a promising candidate for the fabrication of flexible cold cathodes.

Effect of hydrogen on the mechanical properties of titanium and its alloys

NASA Technical Reports Server (NTRS)

Beck, F. H.

1975-01-01

Occluded hydrogen resulting from cathodic charging of commercially pure titanium and titanium alloys, Ti-8Al-1Mo-1V and Ti-6Al-4V, was shown to cause embrittlement of the alloys. Embrittlement was a function of the interstitial hydrogen content rather than the amount of precipitated titanium hydride. The effects of hydrogen concentration on the critical strain for plastic instability along pure shear directions was determined for alloys Ti-8Al-1Mo-1V and Ti-5Al-2.5Sn. Hydrogen, in concentrations below that necessary for spontaneous hydride precipitation, increased the strain necessary for instability formation or instability failure. The strain rate sensitivity also increased with increasing hydrogen concentration. The effect of hydrogen on slip and twinning was determined for titanium single crystals. The critical resolved shear stress for prism slip was increased and the critical resolved shear stress for twinning was decreased with increasing hydrogen concentration.

Crystal habit-tuned nanoplate material of Li[Li1/3-2x/3NixMn2/3-x/3]O₂ for high-rate performance lithium-ion batteries.

PubMed

Wei, Guo-Zhen; Lu, Xia; Ke, Fu-Sheng; Huang, Ling; Li, Jun-Tao; Wang, Zhao-Xiang; Zhou, Zhi-You; Sun, Shi-Gang

2010-10-15

A cathode for high-rate performance lithium-ion batteries (LIBs) has been developed from a crystal habit-tuned nanoplate Li(Li(0.17)Ni(0.25)Mn(0.58))O₂ material, in which the proportion of (010) nanoplates (see figure) has been significantly increased. The results demonstrate that the fraction of the surface that is electrochemically active for Li(+) transportation is a key criterion for evaluating the different nanostructures of potential LIB materials.

Insight into the structure and functional application of the Sr0.95Ce0.05CoO3-δ cathode for solid oxide fuel cells.

PubMed

Yang, Wei; Zhang, Huairuo; Sun, Chunwen; Liu, Lilu; Alonso, J A; Fernández-Díaz, M T; Chen, Liquan

2015-04-06

A new perovskite cathode, Sr0.95Ce0.05CoO3-δ, performs well for oxygen-reduction reactions in solid oxide fuel cells (SOFCs). We gain insight into the crystal structure of Sr1-xCexCoO3-δ (x = 0.05, 0.1) and temperature-dependent structural evolution of Sr0.95Ce0.05CoO3-δ by X-ray diffraction, neutron powder diffraction, and scanning transmission electron microscopy experiments. Sr0.9Ce0.1CoO3-δ shows a perfectly cubic structure (a = a0), with a large oxygen deficiency in a single oxygen site; however, Sr0.95Ce0.05CoO3-δ exhibits a tetragonal perovskite superstructure with a double c axis, defined in the P4/mmm space group, that contains two crystallographically different cobalt positions, with distinct oxygen environments. The structural evolution of Sr0.95Ce0.05CoO3-δ at high temperatures was further studied by in situ temperature-dependent NPD experiments. At 1100 K, the oxygen atoms in Sr0.95Ce0.05CoO3-δ show large and highly anisotropic displacement factors, suggesting a significant ionic mobility. The test cell with a La0.8Sr0.2Ga0.83Mg0.17O3-δ-electrolyte-supported (∼300 μm thickness) configuration yields peak power densities of 0.25 and 0.48 W cm(-2) at temperatures of 1023 and 1073 K, respectively, with pure H2 as the fuel and ambient air as the oxidant. The electrochemical impedance spectra evolution with time of the symmetric cathode fuel cell measured at 1073 K shows that the Sr0.95Ce0.05CoO3-δ cathode possesses superior ORR catalytic activity and long-term stability. Mixed ionic-electronic conduction properties of Sr0.95Ce0.05CoO3-δ account for its good performance as an oxygen-reduction catalyst.

Study of superhydrophobic electrosprayed catalyst layers using a localized reference electrode technique

NASA Astrophysics Data System (ADS)

Chaparro, A. M.; Ferreira-Aparicio, P.; Folgado, M. A.; Brightman, E.; Hinds, G.

2016-09-01

The performance of electrosprayed cathode catalyst layers in a polymer electrolyte membrane fuel cell (PEMFC) is studied using a localized reference electrode technique. Single cells with an electrosprayed cathode catalyst layer show an increase of >20% in maximum power density under standard testing conditions, compared with identical cells assembled with a conventional, state-of-the-art, gas diffusion cathode. When operated at high current density (1.2 A cm-2) the electrosprayed catalyst layers show more homogeneous distribution of the localized cathode potential, with a standard deviation from inlet to outlet of <50 mV, compared with 79 mV for the conventional gas diffusion cathode. Higher performance and homogeneity of cell response is attributed to the superhydrophobic nature of the macroporous electrosprayed catalyst layer structure, which enhances the rate of expulsion of liquid water from the cathode. On the other hand, at low current densities (<0.5 A cm-2), the electrosprayed layers exhibit more heterogeneous distribution of cathode potential than the conventional cathodes; this behavior is attributed to less favorable kinetics for oxygen reduction in very hydrophobic catalyst layers. The optimum performance may be obtained with electrosprayed catalyst layers employing a high Pt/C catalyst ratio.

High intensity, plasma-induced electron emission from large area carbon nanotube array cathodes

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

Liao Qingliang; Yang Ya; Qi Junjie

2010-02-15

The plasma-induced electron emission properties of large area carbon nanotube (CNT) array cathodes under different pulse electric fields were investigated. The formation and expansion of cathode plasmas were proved; in addition, the cathodes have higher emission current in the double-pulse mode than that in the single-pulse mode due to the expansion of plasma. Under the double-pulse electric field of 8.16 V/mum, the plasma's expansion velocity is about 12.33 cm/mus and the highest emission current density reached 107.72 A/cm{sup 2}. The Cerenkov radiation was used to diagnose the distribution of electron beams, and the electron beams' generating process was plasma-induced emission.

Cathode surface effects and H.F.-behaviour of vacuum arcs

NASA Astrophysics Data System (ADS)

Fu, Yan Hong

To gain a better understanding of the essential processes occurring during a vacuum arc interruption for the further development of the vacuum arc circuit breaker, cathode spot behavior, current interruption, dielectrical recovery and overvoltage generation are investigated. An experimental study on cathode spot behavior of the DC vacuum arc in relation to cathode surface roughness and a qualitative physical model to interpret the results are reported. An experimental investigation on the High Frequency (HF) current interruption, multiple recognitions and voltage escalation phenomena is reported. A calculation program to predict the level of overvoltages generated by the operation of a vacuum breaker in a realistic single phase circuit is developed. Detailed results are summarized.

Microbial stratification structure within cathodic biofilm of the microbial fuel cell using the freezing microtome method.

PubMed

Li, Xiao; Lu, Yaobin; Luo, Haiping; Liu, Guangli; Zhang, Renduo

2017-10-01

The aim of this study was to investigate the microbial stratification structure within cathodic biofilm of the microbial fuel cell (MFC) using the freezing microtome method. Experiments were conducted in a single-chamber air-cathode MFC with 0.8g/L maltodextrin as substrate for ∼30d operation. The maximum power density was 945±10mW/m 2 in the MFC. Maltodextrin resulted in the relative abundance of Candidatus Saccharibacteria of 37.0% in the anodic biofilm. Different bacterial communities were identified in different layers within the cathodic biofilm. The relative abundance of Enterococcus was 3.7%, 10.5%, and 1.6% in the top (100-150μm), middle (50-100μm), and bottom (0-50μm) layers, respectively. Higher bacterial viability was observed within the top and bottom layers of the cathodic biofilm. Understanding the stratification of bacterial community in cathodic biofilm should be important to control the cathodic biofilm in the MFC. Copyright © 2017 Elsevier Ltd. All rights reserved.

GROWTH AND CHARACTERIZATION OF SINGLE CRYSTALS OF RARE EARTH COMPOUNDS.

DTIC Science & Technology

SINGLE CRYSTALS, CRYSTAL GROWTH), (*CRYSTAL GROWTH, SINGLE CRYSTALS), (*RARE EARTH COMPOUNDS, SINGLE CRYSTALS), EPITAXIAL GROWTH, SODIUM COMPOUNDS, CHLORIDES, VAPOR PLATING, ELECTROSTATIC FIELDS, ENERGY, ATOMIC PROPERTIES , BONDING

A multiple-cathode, high-power, rectangular ion thruster discharge chamber of increasing thruster lifetime

NASA Astrophysics Data System (ADS)

Rovey, Joshua Lucas

Ion thrusters are high-efficiency, high-specific impulse space propulsion systems proposed for deep space missions requiring thruster operational lifetimes of 7--14 years. One of the primary ion thruster components is the discharge cathode assembly (DCA). The DCA initiates and sustains ion thruster operation. Contemporary ion thrusters utilize one molybdenum keeper DCA that lasts only ˜30,000 hours (˜3 years), so single-DCA ion thrusters are incapable of satisfying the mission requirements. The aim of this work is to develop an ion thruster that sequentially operates multiple DCAs to increase thruster lifetime. If a single-DCA ion thruster can operate 3 years, then perhaps a triple-DCA thruster can operate 9 years. Initially, a multiple-cathode discharge chamber (MCDC) is designed and fabricated. Performance curves and grid-plane current uniformity indicate operation similar to other thrusters. Specifically, the configuration that balances both performance and uniformity provides a production cost of 194 W/A at 89% propellant efficiency with a flatness parameter of 0.55. One of the primary MCDC concerns is the effect an operating DCA has on the two dormant cathodes. Multiple experiments are conducted to determine plasma properties throughout the MCDC and near the dormant cathodes, including using "dummy" cathodes outfitted with plasma diagnostics and internal plasma property mapping. Results are utilized in an erosion analysis that suggests dormant cathodes suffer a maximum pre-operation erosion rate of 5--15 mum/khr (active DCA maximum erosion is 70 mum/khr). Lifetime predictions indicate that triple-DCA MCDC lifetime is approximately 2.5 times longer than a single-DCA thruster. Also, utilization of new keeper materials, such as carbon graphite, may significantly decrease both active and dormant cathode erosion, leading to a further increase in thruster lifetime. Finally, a theory based on the near-DCA plasma potential structure and propellant flow rate effects is developed to explain active DCA erosion. The near-DCA electric field pulls ions into the DCA such that they bombard and erode the keeper. Charge-exchange collisions between bombarding ions and DCA-expelled neutral atoms reduce erosion. The theory explains ion thruster long-duration wear-test results and suggests increasing propellant flow rate may eliminate or reduce DCA erosion.

Lines in the spectrum of /sup 6/LiD (3086--5156 A)

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

Li, K.C.

1976-01-01

The emission spectra of A/sup 1/..sigma../sup +/--X/sup 1/..sigma../sup +/ bands of /sup 6/LiD were photographed in the 3086 A - 5156 A region with a 3.4 meter Ebert Spectrograph of theoretical resolution of about 0.07 cm/sup -1/. High-purity /sup 6/LiD crystals were obtained from Oak Ridge National Laboratory. The atomic percent of /sup 6/Li in /sup 6/LiD was 95.58 percent. The discharge source is a demountable stainless steel hollow cathode lamp. The lithium deuteride crystals were packed into the cathode. Pressure in the discharge tube was about 10 to 20 torr of D/sub 2/. The discharge was run at aboutmore » 600 volts and 1.25 to 1.75 amperes. Acceptable spectra were obtained with exposure time of 6 hours. A Westinghouse iron hollow cathode was used to produce the iron spectrum for calibration. The plates were measured on the Gaertner photoplate comparator with an encoder system and on-line computer service at Argonne National Laboratory. The measured lines in the spectra of /sup 6/LiD are given in this report (COO-2326-18). Similar spectra for /sup 6/LiH and /sup 7/LiH are given in companion reports (COO-2326-17) and (COO-2326-19), respectively. The relative intensities of the lines are applicable only to short regions and do not extend over the whole spectrum.« less

Lines in the spectrum of /sup 6/LiH (2985--5158 A)

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

Li, K.C.

1976-01-01

The emission spectra of the A/sup 1/..sigma../sup +/--X/sup 1/..sigma../sup +/ bands of /sup 6/LiH were photographed in the 2985 - 5158 A region with a 3.4 meter Ebert Spectrograph of theoretical resolution of about 0.07 cm/sup -1/. High-purity /sup 6/LiH crystals were obtained from Oak Ridge National Laboratory. The atomic percent of /sup 6/Li in /sup 6/LiH was 95.58 percent. The discharge source was a demountable stainless steel hollow cathode lamp. The lithium hydride crystals were packed into the cathode. Pressure in the discharge tube was about 10 to 20 torr of H/sub 2/. The disharge was run at aboutmore » 600 volts and 1.25 to 1.75 amperes. Acceptable spectra were obtained with exposure time of 6 hours. A Westinghouse iron hollow cathode was used to produce the iron spectrum for calibration. The plates were measured on the Gaertner photoplate comparator with an encoder system and on-line computer service at Argonne National Laboratory. The measured lines in the spectra of /sup 6/LiH are given in this report (COO-2326-17). Similar spectra for /sup 6/LiD and /sup 7/LiH are given in companion reports (COO-2326-18) and (COO-2326-19), respectively. The relative intensities of the lines are applicable only to short regions and do not extend over the whole spectrum.« less

Mesoporous LiFeBO3/C hollow spheres for improved stability lithium-ion battery cathodes

NASA Astrophysics Data System (ADS)

Chen, Zhongxue; Cao, Liufei; Chen, Liang; Zhou, Haihui; Zheng, Chunman; Xie, Kai; Kuang, Yafei

2015-12-01

Polyanionic compounds are regarded as one of the most promising cathode materials for the next generation lithium-ion batteries due to their abundant resource and thermal stability. LiFeBO3 has a relatively higher capacity than olivine LiFePO4, however, moisture sensitivity and low conductivity hinder its further development. Here, we design and synthesize mesoporous LiFeBO3/C (LFB/C) hollow spheres to enhance its structural stability and electric conductivity, two LiFeBO3/C electrodes with different carbon content are prepared and tested. The experimental results show that mesoporous LiFeBO3/C hollow spheres with higher carbon content exhibit superior lithium storage capacity, cycling stability and rate capability. Particularly, the LFB/C electrode with higher carbon content demonstrates good structural stability, which can maintain its original crystal structure and Li storage properties even after three months of air exposure at room temperature. The exceptional structural stability and electrochemical performance may justify their potential use as high-performance cathode materials for advanced lithium-ion batteries. In addition, the synthesis strategy demonstrated herein is simple and versatile for the fabrication of other polyanionic cathode materials with mesoporous hollow spherical structure.

Mesoporous carbon-coated LiFePO4 nanocrystals co-modified with graphene and Mg2+ doping as superior cathode materials for lithium ion batteries.

PubMed

Wang, Bo; Xu, Binghui; Liu, Tiefeng; Liu, Peng; Guo, Chenfeng; Wang, Shuo; Wang, Qiuming; Xiong, Zhigang; Wang, Dianlong; Zhao, X S

2014-01-21

In this work, mesoporous carbon-coated LiFePO4 nanocrystals further co-modified with graphene and Mg(2+) doping (G/LFMP) were synthesized by a modified rheological phase method to improve the speed of lithium storage as well as cycling stability. The mesoporous structure of LiFePO4 nanocrystals was designed and realized by introducing the bead milling technique, which assisted in forming sucrose-pyrolytic carbon nanoparticles as the template for generating mesopores. For comparison purposes, samples modified only with graphene (G/LFP) or Mg(2+) doping (LFMP) as well as pure LiFePO4 (LFP) were also prepared and investigated. Microscopic observation and nitrogen sorption analysis have revealed the mesoporous morphologies of the as-prepared composites. X-ray diffraction (XRD) and Rietveld refinement data demonstrated that the Mg-doped LiFePO4 is a single olivine-type phase and well crystallized with shortened Fe-O and P-O bonds and a lengthened Li-O bond, resulting in an enhanced Li(+) diffusion velocity. Electrochemical properties have also been investigated after assembling coin cells with the as-prepared composites as the cathode active materials. Remarkably, the G/LFMP composite has exhibited the best electrochemical properties, including fast lithium storage performance and excellent cycle stability. That is because the modification of graphene provided active sites for nuclei, restricted the in situ crystallite growth, increased the electronic conductivity and reduced the interface reaction current density, while, Mg(2+) doping improved the intrinsically electronic and ionic transfer properties of LFP crystals. Moreover, in the G/LFMP composite, the graphene component plays the role of "cushion" as it could quickly realize capacity response, buffering the impact to LFMP under the conditions of high-rate charging or discharging, which results in a pre-eminent rate capability and cycling stability.

A versatile single molecular precursor for the synthesis of layered oxide cathode materials for Li-ion batteries.

PubMed

Li, Maofan; Liu, Jiajie; Liu, Tongchao; Zhang, Mingjian; Pan, Feng

2018-02-01

A carbonyl-bridged single molecular precursor LiTM(acac) 3 [transition metal (TM) = cobalt/manganese/nickel (Co/Mn/Ni), acac = acetylacetone], featuring a one-dimensional chain structure, was designed and applied to achieve the layered oxide cathode materials: LiTMO 2 (TM = Ni/Mn/Co, NMC). As examples, layered oxides, primary LiCoO 2 , binary LiNi 0.8 Co 0.2 O 2 and ternary LiNi 0.5 Mn 0.3 Co 0.2 O 2 were successfully prepared to be used as cathode materials. When they are applied to lithium-ion batteries (LIBs), all exhibit good electrochemical performance because of their unique morphology and great uniformity of element distribution. This versatile precursor is predicted to accommodate many other metal cations, such as aluminum (Al 3+ ), iron (Fe 2+ ), and sodium (Na + ), because of the flexibility of organic ligand, which not only facilitates the doping-modification of the NMC system, but also enables synthesis of Na-ion layered oxides. This opens a new direction of research for the synthesis of high-performance layered oxide cathode materials for LIBs.

Performance and microbial ecology of air-cathode microbial fuel cells with layered electrode assemblies.

PubMed

Butler, Caitlyn S; Nerenberg, Robert

2010-05-01

Microbial fuel cells (MFCs) can be built with layered electrode assemblies, where the anode, proton exchange membrane (PEM), and cathode are pressed into a single unit. We studied the performance and microbial community structure of MFCs with layered assemblies, addressing the effect of materials and oxygen crossover on the community structure. Four MFCs with layered assemblies were constructed using Nafion or Ultrex PEMs and a plain carbon cloth electrode or a cathode with an oxygen-resistant polytetrafluoroethylene diffusion layer. The MFC with Nafion PEM and cathode diffusion layer achieved the highest power density, 381 mW/m(2) (20 W/m(3)). The rates of oxygen diffusion from cathode to anode were three times higher in the MFCs with plain cathodes compared to those with diffusion-layer cathodes. Microsensor studies revealed little accumulation of oxygen within the anode cloth. However, the abundance of bacteria known to use oxygen as an electron acceptor, but not known to have exoelectrogenic activity, was greater in MFCs with plain cathodes. The MFCs with diffusion-layer cathodes had high abundance of exoelectrogenic bacteria within the genus Geobacter. This work suggests that cathode materials can significantly influence oxygen crossover and the relative abundance of exoelectrogenic bacteria on the anode, while PEM materials have little influence on anode community structure. Our results show that oxygen crossover can significantly decrease the performance of air-cathode MFCs with layered assemblies, and therefore limiting crossover may be of particular importance for these types of MFCs.

Direct observation of antisite defects in LiCoPO4 cathode materials by annular dark- and bright-field electron microscopy.

PubMed

Truong, Quang Duc; Devaraju, Murukanahally Kempaiah; Tomai, Takaaki; Honma, Itaru

2013-10-23

LiCoPO4 cathode materials have been synthesized by a sol-gel route. X-ray diffraction analysis confirmed that LiCoPO4 was well-crystallized in an orthorhombic structure in the Pmna space group. From the high-resolution transmission electron microscopy (HR-TEM) image, the lattice fringes of {001} and {100} are well-resolved. The HR-TEM image and selected area electron diffraction pattern reveal the highly crystalline nature of LiCoPO4 having an ordered olivine structure. The atom-by-atom structure of LiCoPO4 olivine has been observed, for the first time, using high-angle annular dark-field (HAADF) and annual bright-field scanning transmission electron microscopy. We observed the bright contrast in Li columns in the HAADF images and strong contrast in the ABF images, directly indicating the antisite exchange defects in which Co atoms partly occupy the Li sites. The LiCoPO4 cathode materials delivered an initial discharge capacity of 117 mAh/g at a C/10 rate with moderate cyclic performance. The discharge profile of LiCoPO4 shows a plateau at 4.75 V, revealing its importance as a potentially high-voltage cathode. The direct visualization of atom-by-atom structure in this work represents important information for the understanding of the structure of the active cathode materials for Li-ion batteries.

Laser-initiated explosive electron emission from flat germanium crystals

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

Porshyn, V., E-mail: porshyn@uni-wuppertal.de; Mingels, S.; Lützenkirchen-Hecht, D.

2016-07-28

Flat Sb-doped germanium (100) crystals were investigated in the triode configuration under pulsed tunable laser illumination (pulse duration t{sub laser} = 3.5 ns and photon energy hν = 0.54–5.90 eV) and under DC voltages <10{sup 4} V. Large bunch charges up to ∼1 μC were extracted from the cathodes for laser pulses >1 MW/cm{sup 2} corresponding to a high quantum efficiency up to 3.3% and cathode currents up to 417 A. This laser-induced explosive electron emission (EEE) from Ge was characterized by its voltage-, laser power- and hν-sensitivity. The analysis of the macroscopic surface damage caused by the EEE is included as well. Moreover, we have carried out firstmore » direct measurements of electron energy distributions produced during the EEE from the Ge samples. The measured electron spectra hint for electron excitations to the vacuum level of the bulk and emission from the plasma plume with an average kinetic energy of ∼0.8 eV.« less

Pt Electrodes Enable the Formation of μ4-O Centers in MOF-5 from Multiple Oxygen Sources.

PubMed

Li, Minyuan M; Dincă, Mircea

2017-10-04

The μ 4 -O 2- ions in the Zn 4 O(O 2 C-) 6 secondary building units of Zn 4 O(1,4-benzenedicarboxylate) 3 (MOF-5) electrodeposited under cathodic bias can be sourced from nitrate, water, and molecular oxygen when using platinum gauze as working electrodes. The use of Zn(ClO 4 ) 2 ·6H 2 O, anhydrous Zn(NO 3 ) 2 , or anhydrous Zn(CF 3 SO 3 ) 2 as Zn 2+ sources under rigorous control of other sources of oxygen, including water and O 2 , confirm that the source of the μ 4 -O 2- ions can be promiscuous. Although this finding reveals a relatively complicated manifold of electrochemical processes responsible for the crystallization of MOF-5 under cathodic bias, it further highlights the importance of hydroxide intermediates in the formation of the Zn 4 O(O 2 C-R) secondary building units in this iconic material and is illustrative of the complicated crystallization mechanisms of metal-organic frameworks in general.

LiCoPO4 cathode from a CoHPO4·xH2O nanoplate precursor for high voltage Li-ion batteries

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

Choi, Daiwon; Li, Xiaolin; Henderson, Wesley A.

2016-02-01

Highly crystalline LiCoPO4/C cathode has been synthesized without any impurities via single step solid-state reaction using CoHPO4xH2O nanoplates as a precursor obtained by simple precipitation route. The electrochemical test shows specific capacity as high as 125mAh/g at charge/discharge rate of C/10. Synthesis approach for obtaining CoHPO4xH2O nanoplate precursor and final LiCoPO4/C cathode using single step solid-state reaction have been characterized using X-ray diffraction, thermos gravimetric analyses (TGA) – differential scanning calorimetry (DSC), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The electrochemical test and cycling stability using different electrolytes, additive and separator have been investigated.

Photoemission experiments of a large area scandate dispenser cathode

NASA Astrophysics Data System (ADS)

Zhang, Huang; Liu, Xing-guang; Chen, Yi; Chen, De-biao; Jiang, Xiao-guo; Yang, An-min; Xia, Lian-sheng; Zhang, Kai-zhi; Shi, Jin-shui; Zhang, Lin-wen

2010-09-01

A 100-mm-diameter scandate dispenser cathode was tested as a photocathode with a 10 ns Nd:YAG laser (266 nm) on an injector test stand for linear induction accelerators. This thermionic dispenser cathode worked at temperatures ranging from room temperature to 930 °C (below or near the thermionic emission threshold) while the vacuum was better than 4×10 -7 Torr. The laser pulse was synchronized with a 120 ns diode voltage pulse stably and they were in single pulse mode. Emission currents were measured by a Faraday cup. The maximum peak current collected at the anode was about 100 A. The maximum quantum efficiency measured at low laser power was 2.4×10 -4. Poisoning effect due to residual gas was obvious and uninterrupted heating was needed to keep cathode's emission capability. The cathode was exposed to air one time between experiments and recovered after being reconditioned. Photoemission uniformity of the cathode was also explored by changing the laser spot's position.

Nickel-based electrodeposits as potential cathode catalysts for hydrogen production by microbial electrolysis

NASA Astrophysics Data System (ADS)

Mitov, M.; Chorbadzhiyska, E.; Nalbandian, L.; Hubenova, Y.

2017-07-01

The development of cost-effective cathodes, operating at neutral pH and ambient temperatures, is a crucial challenge for the practical application of microbial electrolysis cell (MEC) technology. In this study, NiW and NiMo co-deposits produced by electroplating on Ni-foam are explored as cathodes in MEC. The fabricated electrodes exhibit higher corrosion stability and enhanced electrocatalytic activity towards hydrogen evolution reaction in neutral electrolyte compared to the bare Ni-foam. NiW/Ni-foam electrodes possess six times higher intrinsic catalytic activity, estimated from data obtained by linear voltammetry and chronoamperometry. The newly developed electrodes are applied as cathodes in single-chamber membrane-free MEC reactors, inoculated with wastewater and activated sludge from a municipal wastewater treatment plant. Cathodic hydrogen recovery of 79% and 89% by using NiW and NiMo cathodes, respectively, is achieved at applied voltage of 0.6 V. The obtained results reveal potential for practical application of used catalysts in MEC.

Anode-supported single-chamber solid oxide fuel cell based on cobalt-free composite cathode of Nd0.5Sr0.5Fe0.8Cu0.2O3-δ-Sm0.2Ce0.8O1.9 at intermediate temperatures

NASA Astrophysics Data System (ADS)

Yin, Jie-Wei; Zhang, Chunming; Yin, Yi-Mei; Shi, Huangang; Lin, Ye; Lu, Jun; Ma, Zi-Feng

2015-07-01

As a candidate of cathode material of single-chamber solid oxide fuel cell (SC-SOFC), cobalt-free mixed ionic electronic conductor (MIEC) Nd0.5Sr0.5Fe0.8Cu0.2O3-δ (NSFCu) is synthesized by sol-gel method with ethylene diamine tetraacetic acid and citric acid as co-complexing agents. The XRD shows NSFCu is stable after CO2 treatment and chemical compatible with SDC at high temperatures. CO2-TPD (CO2-temperature programmed desorption) demonstrates both CO2 adsorption and desorption phenomenon on NSFCu surface. However, the polarization resistances (Rp) of NSFCu and SDC (10:4 in weight) composite electrodes showed no decay in 5% CO2. Single cell using N2-O2-CH4 mixed gas (CH4 to O2 ratio = 1.5) as fuel shows maximum power density of 635 mW cm-2 at 700 °C. These results suggest that NSFCu-SDC is a promising composite cathode material for application in single-chamber solid oxide fuel cell.

Precipitation method for barium metaborate (BaB{sub 2}O{sub 4}) synthesis from borax solution

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

Akşener, Eymen; Figen, Aysel Kantürk; Pişkin, Sabriye

2013-12-16

In this study, barium metaborate (BaB{sub 2}O{sub 4}, BMB) synthesis from the borax solution was carried out. BMB currently is used in production of ceramic glazes, luminophors, oxide cathodes as well as additives to pigments for aqueous emulsion paints and also β−BaB{sub 2}O{sub 4} single crystals are the best candidate for fabrication of solid-state UV lasers operating at a wavelength of 200 nm due to excellent nonlinear optical properties. In the present study, synthesis was carried out from the borax solution (Na{sub 2}B{sub 4}O{sub 7⋅}10H{sub 2}O, BDH) and barium chloride (BaCI{sub 2⋅}2H{sub 2}O, Ba) in the glass-batch reactor with stirring.more » The effect of, times (5-15 min), molar ratio [stoich.ration (1.0:2.0), 1.25:2.0, 1.5:2.0, 2.5:2:0, 3.0:2.0, 3.5:2.0,4.0:2.0, 5.0:2.0] and also crystallization time (2-6 hour) on the BMB yield (%) was investigated at 80 °C reaction temperature. It is found that, BMB precipitation synthesis with 90 % yield can be performed from 0.50 molar ration (BDH:Ba), under 80 °C, 15 minute, and 6 hours crystallization time. The structural properties of BMB powders were characterized by using XRD, FT-IR and DTA-TG instrumental analysis technique.« less

Structural Variation of LaMnO3+δ by Oxygen Nonstoichiometry

NASA Astrophysics Data System (ADS)

Niwa, Eiki; Maeda, Hiroki; Hashimoto, Takuya; Mizusaki, Junichiro

2013-07-01

The relationship between oxygen content and crystal structure of LaMnO3+δ, which is mother phase of cathode material for solid oxide fuel cells, has been investigated by X-ray diffraction, thermogravimetry and iodometric titration. It was confirmed that LaMnO3+δ with different oxygen content can be prepared by controlling sintering temperature in static air. Crystal system of LaMnO3.17±0.02 and LaMnO3.13±0.01 at room temperature was rhombohedral with space group of Rbar {3}c, whereas crystal structure of LaMnO3.08±0.01 was orthorhombic whose space group was proposed to be Pmna (No. 53). With increase of oxygen content in LaMnO3+δ, molar volume decreased and higher crystal symmetry was obtained.

Theoretical study of cathode surfaces and high-temperature superconductors

NASA Technical Reports Server (NTRS)

Mueller, Wolfgang

1995-01-01

Calculations are presented for the work functions of BaO on W, Os, Pt, and alloys of Re-W, Os-W, and Ir-W that are in excellent agreement with experiment. The observed emission enhancement for alloy relative to tungsten dispenser cathodes is attributed to properties of the substrate crystal structure and explained by the smaller depolarization of the surface dipole on hexagonal as compared to cubic substrates. For Ba and BaO on W(100), the geometry of the adsorbates has been determined by a comparison of inverse photoemission spectra with calculated densities of unoccupied states based on the fully relativistic embedded cluster approach. Results are also discussed for models of scandate cathodes and the electronic structure of oxygen on W(100) at room and elevated temperatures. A detailed comparison is made for the surface electronic structure of the high-temperature superconductor YBa2Cu3O7 as obtained with non-, quasi-, and fully relativistic cluster calculations.

Structure and transport investigations on lithium-iron-phosphate glasses

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

Banday, Azeem; Sharma, Monika; Murugavel, Sevi, E-mail: murug@physics.du.ac.in

2016-05-23

Cathode materials for Lithium Ion Batteries (LIB’s) are being constantly studied and reviewed especially in the past few decades. LiFePO{sub 4} (LFP) is one of the most potential candidates in the pedigree of cathode materials and has been under extensive study ever since. In this work, we report the synthesis of amorphous analogs of crystallite LFP by conventional melt quenching method. Thermal study by using differential scanning calorimetry (DSC) was used to determine the glass transition T{sub g} and crystallization T{sub c} temperatures on the obtained glass sample Fourier transform infrared (FTIR) absorption spectroscopy is being used to investigate themore » structural properties of the glass sample. The intrinsic electrical conductivity measurements were done using broad-band impedance spectroscopy with wide different temperature ranges. The conduction mechanism is described by non-adiabatic small polaron hopping between nearest neighbors. Based on the obtained results, we suggest that the glassy LFP is more suitable cathode material as compared to its crystalline counterpart.« less

Composition and work function relationship in Os–Ru–W ternary alloys

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

Swartzentruber, Phillip D.; Detisch, Michael J.; Balk, T. John, E-mail: john.balk@uky.edu

2015-03-15

Os–Ru thin films with varying concentrations of W were sputter deposited in order to investigate their structure–property relationships. The films were analyzed with x-ray diffraction to investigate their crystal structures, and a Kelvin probe to investigate their work functions. An Os–Ru–W film with ∼30 at. % W yielded a work function maximum of approximately 5.38 eV. These results align well with other studies that found work function minima from thermionic emission data on M-type cathodes with varying amounts of W in the coatings. Furthermore, the results are consistent with other work explaining energy-level alignment and charge transfer of molecules on metalmore » oxides. This may shed light on the mechanism behind the “anomalous effect” first reported by Zalm et al., whereby a high work function coating results in a low work function for emitting cathode surfaces. An important implication of this work is the potential for the Kelvin probe to evaluate the effectiveness of dispenser cathode coatings.« less

Neutron and gamma detector using an ionization chamber with an integrated body and moderator

DOEpatents

Ianakiev, Kiril D.; Swinhoe, Martyn T.; Lestone, John Paul

2006-07-18

A detector for detecting neutrons and gamma radiation includes a cathode that defines an interior surface and an interior volume. A conductive neutron-capturing layer is disposed on the interior surface of the cathode and a plastic housing surrounds the cathode. A plastic lid is attached to the housing and encloses the interior volume of the cathode forming an ionization chamber, into the center of which an anode extends from the plastic lid. A working gas is disposed within the ionization chamber and a high biasing voltage is connected to the cathode. Processing electronics are coupled to the anode and process current pulses which are converted into Gaussian pulses, which are either counted as neutrons or integrated as gammas, in response to whether pulse amplitude crosses a neutron threshold. The detector according to the invention may be readily fabricated into single or multilayer detector arrays.

Operation of Direct Drive Systems: Experiments in Peak Power Tracking and Multi-Thruster Control

NASA Technical Reports Server (NTRS)

Snyder, John Steven; Brophy, John R.

2013-01-01

Direct-drive power and propulsion systems have the potential to significantly reduce the mass of high-power solar electric propulsion spacecraft, among other advantages. Recent experimental direct-drive work has significantly mitigated or retired the technical risks associated with single-thruster operation, so attention is now moving toward systems-level areas of interest. One of those areas is the use of a Hall thruster system as a peak power tracker to fully use the available power from a solar array. A simple and elegant control based on the incremental conductance method, enhanced by combining it with the unique properties of Hall thruster systems, is derived here and it is shown to track peak solar array power very well. Another area of interest is multi-thruster operation and control. Dualthruster operation was investigated in a parallel electrical configuration, with both thrusters operating from discharge power provided by a single solar array. Startup and shutdown sequences are discussed, and it is shown that multi-thruster operation and control is as simple as for a single thruster. Some system architectures require operation of multiple cathodes while they are electrically connected together. Four different methods to control the discharge current emitted by individual cathodes in this configuration are investigated, with cathode flow rate control appearing to be advantageous. Dual-parallel thruster operation with equal cathode current sharing at total powers up to 10 kW is presented.

Effort towards symmetric removal and surface smoothening of 1.3-GHz niobium single-cell cavity in vertical electropolishing using a unique cathode

NASA Astrophysics Data System (ADS)

Chouhan, Vijay; Kato, Shigeki; Nii, Keisuke; Yamaguchi, Takanori; Sawabe, Motoaki; Hayano, Hitoshi; Ida, Yoshiaki

2017-08-01

A detailed study on vertical electropolishing (VEP) of a 1.3-GHz single-cell niobium coupon cavity, which contains six coupons and four viewports at different positions, is reported. The cavity was vertically electropolished using a conventional rod and three types of unique cathodes named as Ninja cathodes, which were designed to have four retractable blades made of either an insulator or a metal or a combination of both. This study reveals the effect of the cathodes and their rotation speed on uniformity in removal thickness and surface morphology at different positions inside the cavity. Removal thickness was measured at several positions of the cavity using an ultrasonic thickness gauge and the surface features of the coupons were examined by an optical microscope and a surface profiler. The Ninja cathode with partial metallic blades was found to be effective not only in reducing asymmetric removal, which is one of the major problems in VEP and might be caused by the accumulation of hydrogen (H2 ) gas bubbles on the top iris of the cavity, but also in yielding a smooth surface of the entire cavity. A higher rotation speed of the Ninja cathode prevents bubble accumulation on the upper iris, and might result in a viscous layer of similar thickness in the cavity cell. Moreover, a higher electric field at the equator owing to the proximity of partial metallic blades to the equator surface resulted in a smooth surface. The effects of H2 gas bubbles and stirring were also observed in lab EP experiments.

Bio-recognition and detection using liquid crystals.

PubMed

Hussain, A; Pina, A S; Roque, A C A

2009-09-15

Liquid crystals (LCs) are used extensively by the electronics industry as display devices. Advances in the understanding of the liquid crystalline phase and the chemistry therein lead to the development of LC exhibiting faster switching speed with greater twist angle. This in turn lead to the emergence of liquid crystal displays, rendering dial-and-needle based displays (such as those used in various meters) and cathode ray tubes obsolete. In this article, we review the history of LC and their emergence as an invaluable material for display devices and the more recent discovery of their use as sensing elements in biosensors. This new application of LC as tools in the development of fast and simple biosensors is envisaged to gain more importance in the foreseeable future.

Efficient removal of nitrobenzene and concomitant electricity production by single-chamber microbial fuel cells with activated carbon air-cathode.

PubMed

Zhang, Enren; Wang, Feng; Zhai, Wenjing; Scott, Keith; Wang, Xu; Diao, Guowang

2017-04-01

Single-chamber microbial fuel cells (S-MFCs) with bio-anodes and activated carbon (AC) air-cathodes showed high nitrobenzene (NB) tolerance and NB removal with concomitant electricity production. The maximum power over 25Wm -3 could be obtained when S-MFCs were operated in the NB loading range of 1.2-6.2molm -3 d -1 , and stable electricity production over 13.7Wm -3 could be produced in a NB loading range of 1.2-14.7molm -3 d -1 . The present S-MFCs exhibited high NB removal performance with NB removal efficiency over 97% even when the NB loading rate was increased to 17.2molm -3 d -1 . The potential NB reduced product (i.e. aniline) could also be effectively removed from influents. The findings in this study means that single-chamber MFCs assembled with pre-enriched bio-anodes and AC air-cathodes could be developed as effective bio-electrochemical systems to remove NB from wastewaters and to harvest energy instead of consuming energy. Copyright © 2017 Elsevier Ltd. All rights reserved.

Solid oxide fuel cell cathode with oxygen-reducing layer

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

Surdoval, Wayne A.; Berry, David A.; Shultz, Travis

The disclosure provides a SOFC comprised of an electrolyte, anode, and cathode, where the cathode comprises an MIEC and an oxygen-reducing layer. The oxygen-reducing layer is in contact with the MIEC, and the MIEC is generally between and separating the oxygen-reducing layer and the electrolyte. The oxygen-reducing layer is comprised of single element oxides, single element carbonates, or mixtures thereof, and has a thickness of less than about 30 nm. In a particular embodiment, the thickness is less than 5 nm. In another embodiment, the thickness is about 3 monolayers or less. The oxygen-reducing layer may be a continuous filmmore » or a discontinuous film with various coverage ratios. The oxygen-reducing layer at the thicknesses described may be generated on the MIEC surface using means known in the art such as, for example, ALD processes.« less

Full cell simulation and the evaluation of the buffer system on air-cathode microbial fuel cell

NASA Astrophysics Data System (ADS)

Ou, Shiqi; Kashima, Hiroyuki; Aaron, Douglas S.; Regan, John M.; Mench, Matthew M.

2017-04-01

This paper presents a computational model of a single chamber, air-cathode MFC. The model considers losses due to mass transport, as well as biological and electrochemical reactions, in both the anode and cathode half-cells. Computational fluid dynamics and Monod-Nernst analysis are incorporated into the reactions for the anode biofilm and cathode Pt catalyst and biofilm. The integrated model provides a macro-perspective of the interrelation between the anode and cathode during power production, while incorporating microscale contributions of mass transport within the anode and cathode layers. Model considerations include the effects of pH (H+/OH- transport) and electric field-driven migration on concentration overpotential, effects of various buffers and various amounts of buffer on the pH in the whole reactor, and overall impacts on the power output of the MFC. The simulation results fit the experimental polarization and power density curves well. Further, this model provides insight regarding mass transport at varying current density regimes and quantitative delineation of overpotentials at the anode and cathode. Overall, this comprehensive simulation is designed to accurately predict MFC performance based on fundamental fluid and kinetic relations and guide optimization of the MFC system.

Characterization of physio-chemical properties of polymeric and electrochemical materials for aerospace flight

NASA Technical Reports Server (NTRS)

Rock, M.; Kunigahalli, V.; Khan, S.; Mcnair, A.

1984-01-01

Sealed nickel cadmium cells having undergone a large number of cycles were discharged using the Hg/HgO reference electrode. The negative electrode exhibited the second plateau. SEM of negative plates of such cells show clusters of large crystals of cadmium hydroxide. These large crystals on the negative plates disappear after continuous overcharging in flooded cells. Atomic Absorption Spectroscopy and standard wet chemical methods are being used to determine the cell materials viz: nickel, cadmium, cobalt, potassum and carbonate. The anodes and cathodes are analyzed after careful examination and the condition of the separator material is evaluated.

Synthesis of LiMn1.9Ti0.09Si0.01O4 by self-propagating combustion method

NASA Astrophysics Data System (ADS)

Abdullah, Amzar Ahlami; Kamarulzaman, Norlida; Badar, Nurhanna; Aziz, Nor Diyana Abdul

2017-09-01

Cathode materials have been an essential area of research for many decades. In this work, a novel spinel cathode, LiMn1.9Ti0.09Si0.01O4 was prepared via a combustion method using citric acid as a reductant. The objective is to obtain a pure and single phase cubic structured material. The precursors obtained were annealed at 600, 700 and 800 °C for 24 hours. The observed materials were characterized by thermal profiling and X-ray diffraction. Pure and single phase materials are obtained and achieved.

Surface and bulk modified high capacity layered oxide cathodes with low irreversible capacity loss

NASA Technical Reports Server (NTRS)

Manthiram, Arumugam (Inventor); Wu, Yan (Inventor)

2010-01-01

The present invention includes compositions, surface and bulk modifications, and methods of making of (1-x)Li[Li.sub.1/3Mn.sub.2/3]O.sub.2.xLi[Mn.sub.0.5-yNi.sub.0.5-yCo.sub.2- y]O.sub.2 cathode materials having an O3 crystal structure with a x value between 0 and 1 and y value between 0 and 0.5, reducing the irreversible capacity loss in the first cycle by surface modification with oxides and bulk modification with cationic and anionic substitutions, and increasing the reversible capacity to close to the theoretical value of insertion/extraction of one lithium per transition metal ion (250-300 mAh/g).

cathode material for Li-ion batteries

NASA Astrophysics Data System (ADS)

Wang, Yanming; Wang, Yajing; Wang, Fei

2014-05-01

Well-crystallized Li2NiTiO4 nanoparticles are rapidly synthesized by a molten salt method using a mixture of NaCl and KCl salts. X-ray diffraction pattern and scanning electron microscopic image show that Li2NiTiO4 has a cubic rock salt structure with an average particle size of ca. 50 nm. Conductive carbon-coated Li2NiTiO4 is obtained by a facile ball milling method. As a novel 4 V positive cathode material for Li-ion batteries, the Li2NiTiO4/C delivers high discharge capacities of 115 mAh g-1 at room temperature and 138 mAh g-1 and 50°C, along with a superior cyclability.

Theoretical study of cathode surfaces and high-temperature superconductors

NASA Technical Reports Server (NTRS)

Mueller, Wolfgang

1994-01-01

The surface-dipole properties of model cathode surfaces have been investigated with relativistic scattered-wave cluster calculations. Work-function/coverage curves have been derived from these data by employing the depolarization model of interacting surface dipoles. Accurate values have been obtained for the minimum work functions of several low-work-function surfaces. In the series BaO on bcc W, hcp Os, and fcc Pt, BaO/Os shows a lower and BaO/Pt a higher work function than BaO/W, which is attributed to the different substrate crystal structures involved. Results are also presented on the electronic structure of the high-temperature superconductor YBa2Cu3O7, which has been investigated with fully relativistic calculations for the first time.

Hollow nanoparticle cathode materials for sodium electrochemical cells and batteries

DOEpatents

Shevchenko, Elena; Rajh, Tijana; Johnson, Christopher S.; Koo, Bonil

2016-07-12

A cathode comprises, in its discharged state, a layer of hollow .gamma.-Fe.sub.2O.sub.3 nanoparticles disposed between two layers of carbon nanotubes, and preferably including a metallic current collector in contact with one of the layers of carbon nanotubes. Individual particles of the hollow .gamma.-Fe.sub.2O.sub.3 nanoparticles comprise a crystalline shell of .gamma.-Fe.sub.2O.sub.3 including cation vacancies within the crystal structure of the shell (i.e., iron vacancies of anywhere between 3% to 90%, and preferably 44 to 77% of available octahedral iron sites). Sodium ions are intercalated within at least some of the cation vacancies within the crystalline shell of the hollow .gamma.-Fe.sub.2O.sub.3 nanoparticles.

Surface and bulk modified high capacity layered oxide cathodes with low irreversible capacity loss

DOEpatents

Manthiram, Arumugam; Wu, Yan

2010-03-16

The present invention includes compositions, surface and bulk modifications, and methods of making of (1-x)Li[Li.sub.1/3Mn.sub.2/3]O.sub.2.xLi[Mn.sub.0.5-yNi.sub.0.5-yCo.sub.2- y]O.sub.2 cathode materials having an O3 crystal structure with a x value between 0 and 1 and y value between 0 and 0.5, reducing the irreversible capacity loss in the first cycle by surface modification with oxides and bulk modification with cationic and anionic substitutions, and increasing the reversible capacity to close to the theoretical value of insertion/extraction of one lithium per transition metal ion (250-300 mAh/g).

Aligned Li+ Tunnels in Core-Shell Li(NixMnyCoz)O2@LiFePO4 Enhances Its High Voltage Cycling Stability as Li-ion Battery Cathode.

PubMed

Wu, Zhongzhen; Ji, Shunping; Liu, Tongchao; Duan, Yandong; Xiao, Shu; Lin, Yuan; Xu, Kang; Pan, Feng

2016-10-12

Layered transition-metal oxides (Li[Ni x Mn y Co z ]O 2 , NMC, or NMCxyz) due to their poor stability when cycled at a high operating voltage (>4.5 V) have limited their practical applications in industry. Earlier researches have identified Mn(II)-dissolution and some parasitic reactions between NMC surface and electrolyte, especially when NMC is charged to a high potential, as primarily factors responsible for the fading. In our previous work, we have achieved a capacity of NMC active material close to theoretical value and optimized its cycling performance by a depolarized carbon nanotubes (CNTs) network and an unique "pre-lithiation process" that generates an in situ organic coating (∼40 nm) to prevent Mn(II) dissolution and minimize the parasitic reactions. Unfortunately, this organic coating is not durable enough during a long-term cycling when the cathode operates at a high potential (>4.5 V). This work attempts to improve the surface protection of the NMC532 particles by applying an active inorganic coating consisting of nanosized- and crystal-orientated LiFePO 4 (LFP) (about 50 nm, exposed (010) face) to generate a core-shell nanostructure of Li(Ni x Mn y Co z )O 2 @LiFePO 4 . Transmission electron microscopy (TEM) and etching X-ray photoelectron spectroscopy have confirmed an intimate contact coating (about 50 nm) between the original structure of NMC and LFP single-particle with atomic interdiffusion at the core-shell interface, and an array of interconnected aligned Li + tunnels are observed at the interface by cross-sectional high-resolution TEM, which were formed by ball-milling and then strictly controlling the temperature below 100 °C. Batteries based on this modified NMC cathode material show a high reversible capacity when cycled between 3.0 and 4.6 V during a long-term cycling.

Li2S/Carbon Nanocomposite Strips from a Low-Temperature Conversion of Li2SO4 as High-Performance Lithium-Sulfur Cathodes

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

Ye, Fangmin; Noh, Hyungjun; Lee, Jin Hong

2018-03-12

Carbothermal conversion of Li2SO4 provides a cost-effective strategy to fabricate high-capacity Li2S cathodes, however, Li2S cathodes derived from Li2SO4 at high temperatures (> 800 oC), having high crystallinity and large crystal size, result in a low utilization of Li2S. Here, we report a Li2SO4/poly(vinyl alcohol)-derived Li2S/Carbon nanocomposite (Li2S@C) strips at a record low temperature of 635 oC. These Li2S@C nanocomposite strips as a cathode shows a low initial activation potential (2.63 V), a high initial discharge capacity (805 mAh g-1 Li2S) and a high cycling stability (0.2 C and 1 C). These improvedresults could be ascribed to the nano-sized Li2Smore » particles as well as their low crystallinity due to the PVA-induced carbon network and the low conversion temperature, respectively. An XPS analysis reveals that the C=C and C=O bonds derived from the carbonization of PVA can promote the conversion of Li2SO4 at the low temperature.« less

A new high-energy cathode for a Na-ion battery with ultrahigh stability.

PubMed

Park, Young-Uk; Seo, Dong-Hwa; Kwon, Hyung-Soon; Kim, Byoungkook; Kim, Jongsoon; Kim, Haegyeom; Kim, Inkyung; Yoo, Han-Ill; Kang, Kisuk

2013-09-18

Large-scale electric energy storage is a key enabler for the use of renewable energy. Recently, the room-temperature Na-ion battery has been rehighlighted as an alternative low-cost technology for this application. However, significant challenges such as energy density and long-term stability must be addressed. Herein, we introduce a novel cathode material, Na1.5VPO4.8F0.7, for Na-ion batteries. This new material provides an energy density of ~600 Wh kg(-1), the highest value among cathodes, originating from both the multielectron redox reaction (1.2 e(-) per formula unit) and the high potential (~3.8 V vs Na(+)/Na) of the tailored vanadium redox couple (V(3.8+)/V(5+)). Furthermore, an outstanding cycle life (~95% capacity retention for 100 cycles and ~84% for extended 500 cycles) could be achieved, which we attribute to the small volume change (2.9%) upon cycling, the smallest volume change among known Na intercalation cathodes. The open crystal framework with two-dimensional Na diffusional pathways leads to low activation barriers for Na diffusion, enabling excellent rate capability. We believe that this new material can bring the low-cost room-temperature Na-ion battery a step closer to a sustainable large-scale energy storage system.

Evaluation of pulsed laser deposited SrNb0.1Co0.9O3-δ thin films as promising cathodes for intermediate-temperature solid oxide fuel cells

NASA Astrophysics Data System (ADS)

Chen, Dengjie; Chen, Chi; Gao, Yang; Zhang, Zhenbao; Shao, Zongping; Ciucci, Francesco

2015-11-01

SrNb0.1Co0.9O3-δ (SNC) thin films prepared on single-crystal yttria-stabilized zirconia (YSZ) electrolytes are evaluated as promising cathodes for intermediate-temperature solid oxide fuel cells (IT-SOFCs). Geometrically well-defined polycrystalline SNC thin films with low surface roughness and high surface oxygen vacancy concentration are successfully fabricated by pulsed laser deposition. The thin films are characterized by basic techniques, e.g., X-ray diffraction for phase structure identification, scanning electron microscopy and atomic force microscopy for microstructures measurement, and X-ray photoelectron spectroscopy for elements quantification. Electrochemical impedance spectroscopy (EIS) is used to investigate oxygen reduction reaction activities of SNC thin films in symmetric electrochemical cells. Current collectors (Ag paste, Ag strip, and Au strip) are found to have negligible impact on polarization resistances. A slight decrease of the electrode polarization resistances is observed after adding a samarium doped ceria (SDC) buffer layer between SNC and YSZ. SNC thin-film electrodes exhibit low electrode polarization resistances, e.g., 0.237 Ω cm2 (SNC/SDC/YSZ/SDC/SNC) and 0.274 Ω cm2 (SNC/YSZ/SNC) at 700 °C and 0.21 atm, demonstrating the promise of SNC materials for IT-SOFCs. An oxygen reduction reaction mechanism of SNC thin films is also derived by analyzing EIS at temperature of 550-700 °C under oxygen partial pressure range of 0.04-1 atm.

Sponge-like nanoporous single crystals of gold

PubMed Central

Khristosov, Maria Koifman; Bloch, Leonid; Burghammer, Manfred; Kauffmann, Yaron; Katsman, Alex; Pokroy, Boaz

2015-01-01

Single crystals in nature often demonstrate fascinating intricate porous morphologies rather than classical faceted surfaces. We attempt to grow such crystals, drawing inspiration from biogenic porous single crystals. Here we show that nanoporous single crystals of gold can be grown with no need for any elaborate fabrication steps. These crystals are found to grow following solidification of a eutectic composition melt that forms as a result of the dewetting of nanometric thin films. We also present a kinetic model that shows how this nano-porous single-crystalline structure can be obtained, and which allows the potential size of the porous single crystal to be predicted. Retaining their single-crystalline nature is due to the fact that the full crystallization process is faster than the average period between two subsequent nucleation events. Our findings clearly demonstrate that it is possible to form single-crystalline nano porous metal crystals in a controlled manner. PMID:26554856

Effect of boric acid on the properties of Li{sub 2}MnO{sub 3}·LiNi{sub 0.5}Mn{sub 0.5}O{sub 2} composite cathode powders prepared by large-scale spray pyrolysis with droplet classifier

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

Hong, Young Jun; Choi, Seung Ho; Sim, Chul Min

2012-12-15

Graphical abstract: Display Omitted Highlights: ► Spherical shape Li{sub 2}MnO{sub 3}·LiNi{sub 0.5}Mn{sub 0.5}O{sub 2} composite cathode powders are prepared by large-scale spray pyrolysis with droplet classifier. ► Boric acid improves the morphological and electrochemical properties of the composite cathode powders. ► The discharge capacity of the composite cathode powders decreases from 217 to 196 mAh g{sup −1} by the 30th cycle. -- Abstract: Spherically shaped 0.3Li{sub 2}MnO{sub 3}·0.7LiNi{sub 0.5}Mn{sub 0.5}O{sub 2} composite cathode powders with filled morphology and narrow size distribution are prepared by large-scale spray pyrolysis. A droplet classification reduces the standard deviation of the size distribution of themore » composite cathode powders. Addition of boric acid improves the morphological properties of the product powders by forming a lithium borate glass material with low melting temperature. The optimum amount of boric acid dissolved in the spray solution is 0.8 wt% of the composite powders. The powders prepared from the spray solution with 0.8 wt% boric acid have a mixed layered crystal structure comprising Li{sub 2}MnO{sub 3} and LiNi{sub 0.5}Mn{sub 0.5}O{sub 2} phases, thus forming a composite compound. The initial charge and discharge capacities of the composite cathode powders prepared from the 0.8 wt% boric acid spray solution are 297 and 217 mAh g{sup −1}, respectively. The discharge capacity of the powders decreases from 217 to 196 mAh g{sup −1} by the 30th cycle, in which the capacity retention is 90%.« less

Quantification of the internal resistance distribution of microbial fuel cells.

PubMed

Fan, Yanzhen; Sharbrough, Evan; Liu, Hong

2008-11-01

Identifying the limiting factors in a microbial fuel cell (MFC) system requires qualifying the contribution of each component of an MFC to internal resistance. In this study, a new method was developed to calculate the internal resistance distribution of an MFC. Experiments were conducted to identify the limiting factors in single-chamber MFCs by varying the anode surface areas, cathode surface areas, and phosphate buffer concentrations. For the MFCs with equally sized electrodes (7 cm2) and 200 mM phosphate buffer, the anode contributed just 5.4% of the internal resistance, while the cathode and the electrolyte each contributed 47.3%, indicating that the anode was not the limiting factor in power generation. The limitation of the cathode was further revealed by the 780% higher area-specific resistance (284.4 omega cm2) than the 32.3 omega cm2 of the anode. The electrolyte limitation was also evidenced by the greatly increased contribution of electrolyte in internal resistance from 47.3 to 78.2% when the concentration of phosphate buffer was decreased from 200 to 50 mM. An anodic power density of 6860 mW/m2 was achieved at a current density of 2.62 mA/cm2 using the MFCs with an anode/cathode area ratio of 1/14 and 200 mM phosphate buffer. The method was also successfully applied to analyze the internal resistance distribution of the two chamber MFCs from a previously reported study. The comparison of the internal resistances of the two air cathode systems indicates that the much lower resistances, including anode, cathode, and membrane resistances, contributed to the much better performance of the single-chamber MFCs than the two-chamber system.

Experimental advances and preliminary mathematical modeling of the Swiss-roll mixed-reactant direct borohydride fuel cell

NASA Astrophysics Data System (ADS)

Aziznia, Amin; Oloman, Colin W.; Gyenge, Előd L.

2014-11-01

The Swiss-roll single-cell mixed reactant (SR-MRFC) borohydride - oxygen fuel cell equipped with Pt/carbon cloth 3D anode and either MnO2 or Ag gas-diffusion cathodes is investigated by a combination of experimental studies and preliminary mathematical modeling of the polarization curve. We investigate the effects of four variables: cathode side metallic mesh fluid distributor, separator type (Nafion 112® vs. Viledon®), cathode catalyst (MnO2 vs. Ag), and the hydrophilic pore volume fraction of the gas-diffusion cathode. Using a two-phase feed of alkaline borohydride solution (1 M NaBH4 - 2 M NaOH) and O2 gas in an SR-MRFC equipped with Pt/C 3D anode, MnO2 gas diffusion cathode, Viledon® porous diaphragm, expanded mesh cathode-side fluid distributor, the maximum superficial power density is 2230 W m-2 at 323 K and 105 kPa(abs). The latter superficial power density is almost 3.5 times higher than our previously reported superficial power density for the same catalyst combinations. Furthermore, with a Pt anode and Ag cathode catalyst combination, a superficial power density of 2500 W m-2 is achieved with superior performance durability compared to the MnO2 cathode. The fuel cell results are substantiated by impedance spectroscopy analysis and preliminary mathematical model predictions based on mixed potential theory.

Kinetics of oxygen reduction in perovskite cathodes for solid oxide fuel cells: A combined modeling and experimental approach

NASA Astrophysics Data System (ADS)

Miara, Lincoln James

Solid oxide fuel cells (SOFCs) have the potential to replace conventional stationary power generation technologies; however, there are major obstacles to commercialization, the most problematic of which is poor cathode performance. Commercialization of SOFCs will follow when the mechanisms occurring at the cathode are more thoroughly understood and adapted for market use. The catalytic reduction of oxygen occurring in SOFC cathodes consists of many elementary steps such as gas phase diffusion, chemical and/or electrochemical reactions which lead to the adsorption and dissociation of molecular oxygen onto the cathode surface, mass transport of oxygen species along the surface and/or through the bulk of the cathode, and full reduction and incorporation of the oxygen at the cathode/electrolyte two or three phase boundary. Electrochemical impedance spectroscopy (EIS) is the main technique used to identify the occurrence of these different processes, but when this technique is used without an explicit model describing the kinetics it is difficult to unravel the interdependence of each of these processes. The purpose of this dissertation is to identify the heterogeneous reactions occurring at the cathode of an SOFC by combining experimental EIS results with mathematical models describing the time dependent behavior of the system. This analysis is performed on two different systems. In the first case, experimental EIS results from patterned half cells composed of Ca-doped lanthanum manganite (LCM)| yttria-doped ZrO2 (YSZ) are modeled to investigate the temperature and partial pressure of oxygen, pO2, dependence of oxygen adsorption/dissociation onto the LCM surface, surface diffusion of atomic oxygen, and electrochemical reduction and incorporation of the oxygen into the electrolyte in the vicinity of the triple phase boundary (TPB). This model determines the time-independent state-space equations from which the Faradaic admittance transfer function is obtained. The unknown rate constants (kad, k des, k1, k1¯ ), and parameters (Ds, Q°, n) arising from the governing equations are estimated from a combination of experiments, mathematical analysis, and numerical data analysis. In the second system, dense patterned films of cathode with composition: La0.6Sr0.4Co0.2Fe0.8O3-delta (LSCF-6428) were fabricated on Ga-doped CeO2 coated YSZ substrates. These samples were analyzed by EIS over a temperature and pO 2 range of 600--800 °C and 10-3--1.00 atm, respectively. To understand the EIS results, a 2-dimensional model was developed which accounted for surface oxygen exchange, and both surface and bulk transport of oxygen to the electrolyte interface. The results were obtained by numerically solving a stationary partial differential equation describing the oxygen vacancy distribution in the cathode. From these results, the model impedance was derived and then fitted to the experimental EIS results. From the fitting results the contributions to the impedance from each of the processes were estimated. Also, the surface exchange rate was estimated over the experimental operating conditions. Finally, the results suggest that the surface diffusion occurred by an interstitial type mechanism in this material. The cathode surface is intimately involved in most of the oxygen reduction processes; however, the surface structure and chemistry is typically treated as an extension of the bulk without consideration of the actual surface properties. Recent evidence suggests that significant changes occur to the surface during operation which in turn leads to changes in electrochemical performance. To investigate these phenomena, well-oriented thin films (250 nm in thickness) of Sr-doped lanthanum manginite (LSM) films were grown on single crystals of YSZ (111). Films which were cathodically biased with a -1 V applied dc potential were compared to control samples. The cathodic bias results in both an enhancement in electrochemical performance and a change in surface chemistry. The changes in electrochemical performance were monitored by ES, while the surface changes were tracked with a combination of soft x-ray techniques such as x-ray photoemission spectroscopy and x-ray absorption spectroscopy. The soft x-ray results indicated that the removal of surface passivating phases (i.e., SrO and MnO) are correlated with improved performance. This work demonstrates the success of estimating fundamental parameters, such as diffusivity and surface coverage, from experimental EIS results using a physically realistic model without, as is commonly done, assuming a specific rate limiting step or using an ambiguous equivalent circuit. This allows researchers to fabricate designer cathodes by selecting materials with optimal kinetic properties such as rapid oxygen dissociation and rapid oxygen transport in (or on) the cathode, independent of geometry.

AMLCD head-down displays for avionic applications

NASA Astrophysics Data System (ADS)

Davis, Alan J.

1997-02-01

Smiths Industries has been involved in the design, manufacture and supply of products used for the presentation of information, in one form or another, from its early pioneering years through to the present day. In the mid 1980s Smiths Industries began to invest in the then emerging active matrix liquid crystal display (AMLCD) technology which the company believed would eventually take over from the cathode ray tube. To date Smiths Industries has made a significant investment in acquiring the enabling technology needed to produce active matrix liquid crystal color head- down displays for fast jet, helicopter and civil aircraft applications. The significant improvement in AMLCD product quality and manufacturing capability over recent years has enabled market penetration of AMLCD technology products to be achieved in military and civil avionic markets. Virtually all new contracts for head-down displays are now demanding the use of AMLCD technology rather than the cathode ray tube. A significant decision to move to AMLCD technology was made by McDonnell Douglas Helicopters in 1995, when a contract to supply over 4000 head-down display products for the Apache Helicopter was let. This has paved the way for the future of AMLCD technology.

Growth of single crystals of BaFe12O19 by solid state crystal growth

NASA Astrophysics Data System (ADS)

Fisher, John G.; Sun, Hengyang; Kook, Young-Geun; Kim, Joon-Seong; Le, Phan Gia

2016-10-01

Single crystals of BaFe12O19 are grown for the first time by solid state crystal growth. Seed crystals of BaFe12O19 are buried in BaFe12O19+1 wt% BaCO3 powder, which are then pressed into pellets containing the seed crystals. During sintering, single crystals of BaFe12O19 up to ∼130 μm thick in the c-axis direction grow on the seed crystals by consuming grains from the surrounding polycrystalline matrix. Scanning electron microscopy-energy dispersive spectroscopy analysis shows that the single crystal and the surrounding polycrystalline matrix have the same chemical composition. Micro-Raman scattering shows the single crystal to have the BaFe12O19 structure. The optimum growth temperature is found to be 1200 °C. The single crystal growth behavior is explained using the mixed control theory of grain growth.

Scalable air cathode microbial fuel cells using glass fiber separators, plastic mesh supporters, and graphite fiber brush anodes.

PubMed

Zhang, Xiaoyuan; Cheng, Shaoan; Liang, Peng; Huang, Xia; Logan, Bruce E

2011-01-01

The combined use of brush anodes and glass fiber (GF1) separators, and plastic mesh supporters were used here for the first time to create a scalable microbial fuel cell architecture. Separators prevented short circuiting of closely-spaced electrodes, and cathode supporters were used to avoid water gaps between the separator and cathode that can reduce power production. The maximum power density with a separator and supporter and a single cathode was 75 ± 1 W/m(3). Removing the separator decreased power by 8%. Adding a second cathode increased power to 154 ± 1 W/m(3). Current was increased by connecting two MFCs connected in parallel. These results show that brush anodes, combined with a glass fiber separator and a plastic mesh supporter, produce a useful MFC architecture that is inherently scalable due to good insulation between the electrodes and a compact architecture. Copyright © 2010 Elsevier Ltd. All rights reserved.

Commercial materials as cathode for hydrogen production in microbial electrolysis cell.

PubMed

Farhangi, Sara; Ebrahimi, Sirous; Niasar, Mojtaba Shariati

2014-10-01

The use of commercial electrodes as cathodes in a single-chamber microbial electrolysis cell has been investigated. The cell was operated in sequencing batch mode and the performance of the electrodes was compared with carbon cloth containing 0.5 mg Pt cm(-2). Overall H2 recovery [Formula: see text] was 66.7 ± 1.4, 58.7 ± 1.1 and 55.5 ± 1.5 % for Pt/CC, Ni and Ti mesh electrodes, respectively. Columbic efficiencies of the three cathodes were in the same range (74.8 ± 1.5, 77.6 ± 1.7 and 75.7 ± 1.2 % for Pt/CC, Ni and Ti mesh electrodes, respectively). A similar performance for the three cathodes under near-neutral pH and ambient temperature was obtained. The commercial electrodes are much cheaper than carbon cloth containing Pt. Low cost and good performance of these electrodes suggest they are suitable cathode materials for large scale application.

Transparent Carbon Nanotube layers as cathodes in OLEDs

NASA Astrophysics Data System (ADS)

Papadimitratos, Alexios; Nasibulin, Albert; Kauppinen, Esko; Zakhidov, Anvar; Solarno Inc Collaboration; Aalto University Collaboration; UT Dallas Collaboration

2011-03-01

Organic Light Emitting diodes (OLEDs) have attracted high interest in recent years due to their potential use in future lighting and display applications. Reported work on OLEDs traditionally utilizes low work function materials as cathodes that are expensive to fabricate because of the high vacuum processing. Transparent carbon nanotube (CNT) sheets have excellent mechanical and electrical properties. We have already shown earlier that multi-wall (MWCNT) as well as single CNT (SWCNT) sheets can be used as effective anodes in bright OLEDs [,]. The true advantage of using the CNT sheets lies in flexible devices and new architectures with CNT sheet as layers in tandem devices with parallel connection. In this work, we are investigating the possibility of using SWCNT as cathodes in OLEDs. SWCNT sheets have been reported to show lower work function compared to MWCNT. Our work attempts to demonstrate transparent OLED devices with CNT anodes and cathodes. In the process, OLEDs with CNT cathodes have been fabricated in normal and inverted configurations using inorganic oxides (MoO3,ZnO) as invertion layers.

Cathode Formed by Thermal Evaporation of Ba:Al Alloy and Estimations of Barrier Height in an Organic LED

NASA Astrophysics Data System (ADS)

Ding, Lei; Zhang, Fang-Hui

2011-06-01

It is demonstrated that barium and aluminum alloy synthesized by melting in a glass tube under low vacuum is applicable for organic laser emitting diodes (LEDs) as a thin film cathode. The alloy film obtained by the thermal evaporation of pre-synthesized alloy is used in a single-boat organic LED device with the structure: indium tin oxide (ITO)/4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl(NPB)/tris-(8-hydroxyquinoline) aluminum(Alq3)/barium:aluminum alloy. The experimental results show that devices with this alloy film cathode exhibit better current density-voltage-luminance characteristics than those with a conventional pure Al cathode, and more weight of barium in aluminum leads to better performance of the devices. Characteristics of current density versus voltage for the electron-only devices are fitted by the Richardson—Schottky emission model, indicating that the electron injection barrier has a decrease of about 0.3 eV by this alloy cathode.

[Analysis of color gamut of LCD system based on LED backlight with area-controlling technique].

PubMed

Li, Fu-Wen; Jin, Wei-Qi; Shao, Xi-Bin; Zhang, Li-Lei; Wan, Li-Fang

2010-05-01

Color gamut as a significant performance index for display system describes the color reproduction ability IN real scenes. Liquid crystal display (LCD) is the most popular technology in flat panel display. However, conventional cold cathode fluorescent lamp (CCFL) backlight of LCD can not behave high color gamut compared with cathode ray tube (CRT). The common used method of color gamut measuring for LCD system is introduced at the beginning. According to the inner structure and display principle of LCD system, there are three major factors deciding LCD's color gamut: spectral properties of backlight, transmittance properties of color filters and performance of liquid crystal panel. Instead of conventional backlight CCFL, RGB-LED backlight is used for improving color reproduction of LCD display system. Due to the imperfect match between RGB-LED' s spectra and color filter's transmittance, the color filter would reduce the color gamut of LCD system more or less. Therefore, LCD system based on LED backlight with area-control technique is introduced which modifies backlight control signal according to the input signal After analyzing and calculating the spectra of LED backlight which passes through the color filters using method of colorimetry, the area sizes of color gamut triangles of RGB-LED backlight with area-control and RGB-LED backlight without area-control LCD systems are compared and the relationship between color gamut and varying contrast of liquid crystal panel is analyzed. It is indicated that LED backlight with area-control technique can avoid color saturation dropping and have little effects on the contrast variation of liquid crystal panel. In other words, LED backlight with area-control technique relaxes the requirements of both color filter performance and liquid crystal panel. Thus, it is of importance to improve the color gamut of the current LCD system with area-control LED backlight.

Air Force Research Laboratory High Power Electric Propulsion Technology Development

DTIC Science & Technology

2009-10-27

Plasmas in a Coaxial Double Theta Pinch, “ Doctoral Dissertation, Department of Aerospace Engineering, University of Michigan, Ann Arbor, MI, 2008. [6...surpasses the level of DARPA FAST goals. Several evolving propulsion concepts may enable a viable high-power plasma propulsion device suitable for...of PEPL) 5 performance operation with multiple cathodes or in a single- shared cathode configuration [4]. However, the local plasma properties

Fuel cell having dual electrode anode or cathode

DOEpatents

Findl, Eugene

1985-01-01

A fuel cell that is characterized by including a dual electrode anode that is operable to simultaneously electro-oxidize a gaseous fuel and a liquid fuel. In alternative embodiments, a fuel cell having a single electrode anode is provided with a dual electrode cathode that is operable to simultaneously reduce a gaseous oxidant and a liquid oxidant to electro-oxidize a fuel supplied to the cell.

Fuel cell having dual electrode anode or cathode

DOEpatents

Findl, E.

1984-04-10

A fuel cell that is characterized by including a dual electrode anode that is operable to simultaneously electro-oxidize a gaseous fuel and a liquid fuel. In alternative embodiments, a fuel cell having a single electrode anode is provided with a dual electrode cathode that is operable to simultaneously reduce a gaseous oxidant and a liquid oxidant to electro-oxidize a fuel supplied to the cell.

Full cell simulation and the evaluation of the buffer system on air-cathode microbial fuel cell

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

Ou, Shiqi; Kashima, Hiroyuki; Aaron, Douglas S.

This paper presents a computational model of a single chamber, air-cathode MFC. The model considers losses due to mass transport, as well as biological and electrochemical reactions, in both the anode and cathode half-cells. Computational fluid dynamics and Monod-Nernst analysis are incorporated into the reactions for the anode biofilm and cathode Pt catalyst and biofilm. The integrated model provides a macro-perspective of the interrelation between the anode and cathode during power production, while incorporating microscale contributions of mass transport within the anode and cathode layers. Model considerations include the effects of pH (H +/OH – transport) and electric field-driven migrationmore » on concentration overpotential, effects of various buffers and various amounts of buffer on the pH in the whole reactor, and overall impacts on the power output of the MFC. The simulation results fit the experimental polarization and power density curves well. Further, this model provides insight regarding mass transport at varying current density regimes and quantitative delineation of overpotentials at the anode and cathode. Altogether, this comprehensive simulation is designed to accurately predict MFC performance based on fundamental fluid and kinetic relations and guide optimization of the MFC system.« less

Synergistic Effect between LiNi0.5Co0.2Mn0.3O2 and LiFe0.15Mn0.85PO4/C on Rate and Thermal Performance for Lithium Ion Batteries.

PubMed

Sun, Guiyan; Lai, Shaobo; Kong, Xiangbang; Chen, Zhiqiang; Li, Kun; Zhou, Rong; Wang, Jing; Zhao, Jinbao

2018-05-16

A blend cathode has been prepared by mixing both LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523) of high energy density and high specific capacity and LiFe 0.15 Mn 0.85 PO 4 /C (LFMP/C) of excellent thermal stability via a low-speed ball-milling method. The lithium ion batteries using the blend cathode with LFMP/C of optimum percent exhibit better capacity retention after 100 cycles than those using only single NCM523 or LFMP/C. Both theoretical simulation and experimental rate performances demonstrate that the electrochemical property of blend cathode materials is predictable and economical. In addition, the thermal behaviors of blend cathodes are studied by using differential scanning calorimetry analysis. The thermal stability of blend cathode materials behaves better than that of the bare NCM523 accompanied with an electrolyte. It is found that the outstanding rate and thermal performance of the blend cathode is due to the prominent synergistic effect between NCM523 and LFMP/C, and 10% LFMP/C in the blend cathode materials is the most adaptable as considering both electrochemical and thermal properties simultaneously.

Full cell simulation and the evaluation of the buffer system on air-cathode microbial fuel cell

DOE PAGES

Ou, Shiqi; Kashima, Hiroyuki; Aaron, Douglas S.; ...

2017-02-23

This paper presents a computational model of a single chamber, air-cathode MFC. The model considers losses due to mass transport, as well as biological and electrochemical reactions, in both the anode and cathode half-cells. Computational fluid dynamics and Monod-Nernst analysis are incorporated into the reactions for the anode biofilm and cathode Pt catalyst and biofilm. The integrated model provides a macro-perspective of the interrelation between the anode and cathode during power production, while incorporating microscale contributions of mass transport within the anode and cathode layers. Model considerations include the effects of pH (H +/OH – transport) and electric field-driven migrationmore » on concentration overpotential, effects of various buffers and various amounts of buffer on the pH in the whole reactor, and overall impacts on the power output of the MFC. The simulation results fit the experimental polarization and power density curves well. Further, this model provides insight regarding mass transport at varying current density regimes and quantitative delineation of overpotentials at the anode and cathode. Altogether, this comprehensive simulation is designed to accurately predict MFC performance based on fundamental fluid and kinetic relations and guide optimization of the MFC system.« less

Hollow cathode heater development for the Space Station plasma contactor

NASA Technical Reports Server (NTRS)

Soulas, George C.

1993-01-01

A hollow cathode-based plasma contactor has been selected for use on the Space Station. During the operation of the plasma contactor, the hollow cathode heater will endure approximately 12000 thermal cycles. Since a hollow cathode heater failure would result in a plasma contactor failure, a hollow cathode heater development program was established to produce a reliable heater design. The development program includes the heater design, process documents for both heater fabrication and assembly, and heater testing. The heater design was a modification of a sheathed ion thruster cathode heater. Three heaters have been tested to date using direct current power supplies. Performance testing was conducted to determine input current and power requirements for achieving activation and ignition temperatures, single unit operational repeatability, and unit-to-unit operational repeatability. Comparisons of performance testing data at the ignition input current level for the three heaters show the unit-to-unit repeatability of input power and tube temperature near the cathode tip to be within 3.5 W and 44 degrees C, respectively. Cyclic testing was then conducted to evaluate reliability under thermal cycling. The first heater, although damaged during assembly, completed 5985 ignition cycles before failing. Two additional heaters were subsequently fabricated and have completed 3178 cycles to date in an on-going test.

Communication—Improving Intermediate-Temperature Performance of a Screen-Printed LSCF Cathode with Infiltrated LSCF Nanoparticles

DOE PAGES

Si, Fengzhan; Zhang, Guoguang; Huang, Kevin

2016-04-09

Here, the present study investigates the mass loading effect of an infiltrated La 0.6Sr 0.4Co 0.2Fe 0.8O 3-δ (LSCF) nanoparticles (NPs) catalyst on the area-specific polarization resistance (Rp) of a screen-printed porous LSCF cathode for solid oxide fuel cells. The results show that R p of the LSCF-NPs decorated LSCF cathode can be substantially reduced by as much as 89.3% after a single-step impregnation of 1.5 M nitrate solution containing La:Sr:Co:Fe = 0.6:0.4:0.2:0.8 with a mass loading of 3 wt%.

GEIGER-MULLER TYPE COUNTER TUBE

DOEpatents

Fowler, I.L.; Watt, L.A.K.

1959-12-15

A single counter tube capable of responding to a wide range of intensities is described. The counter tube comprises a tubular cathode and an anode extending centrally of the cathode. The spacing between the outer surface of the anode and the inner surface of the cathode is varied along the length of the tube to provide different counting volumes in adjacent portions of the tube. A large counting volume in one portion adjacent to a low-energy absorption window gives adequate sensitivity for measuring lowintensity radiation, while a smaller volume with close electrode spacing is provided in the counter to make possible measurement of intense garnma radiation fields.

Performance of planar single cell lanthanum gallate based solid oxide fuel cells

NASA Astrophysics Data System (ADS)

Maffei, N.; Kuriakose, A. K.

A novel synthesis of high purity, single phase strontium-magnesium doped lanthanum gallate through a nitrate route is described. The prepared powder is formed into planar monolithic elements by uniaxial pressing followed by isostatic pressing and sintering. XRD analysis of the sintered elements reveal no detectable secondary phases. The performance of the electrolyte in solid oxide fuel cells (SOFC) with three different anode/cathode combinations tested at 700°C with respect to the J- V and power density is reported. The data show that the characteristics of this SOFC are strongly dependent on the particular anode/cathode system chosen.

Analysis of the aging/stability process of organic solar cells based on PTB7:[70]PCBM and an alternative free-vacuum deposited cathode: the effect of active layer scaling

NASA Astrophysics Data System (ADS)

Barreiro-Argüelles, Denisse; Ramos-Ortiz, Gabriel; Maldonado, José-Luis L.; Romero-Borja, Daniel; Meneses-Nava, Marco-Antonio; Pérez-Gutiérrez, Enrique

2017-08-01

The PV performance and aging/stability of organic photovoltaic (OPV) devices based on the well-known system PTB7:[70]PCBM and an alternative air-stable electrode deposited at room conditions are fully studied when the active area is scaled by a factor of 25. On the other hand, the aging/stability processes were also studied through single diode model, impedance spectroscopy and light-beam induced current (LBIC) measurements in accordance with the established ISOS-D1 (dark storage) and ISOS-L1 (illumination conditions) protocols. Results are a good indication that the alternative cathode Field's metal (FM) cathode works as an encapsulating material and provides excellent PV performance comparable with the common and costly high-vacuum evaporated Al cathode.

The Experimental Study of Novel Pseudospark Hollow Cathode Plasma Electron Gun

NASA Astrophysics Data System (ADS)

Gu, Xiaowei; Meng, Lin; Sun, Yiqin; Yu, Xinhua

2008-11-01

The high-power microwave devices with plasma-filled have unique properties. One of the major problems associated with plasma-filled microwave sources is that ions from the plasma drift toward the gun regions of the tube. This bombardment is particularly dangerous for the gun, where high-energy ion impacts can damage the cathode surface and degrade its electron emission capabilities. One of the techniques investigated to mitigate this issue is to replace the material cathode with plasma cathode. Now, we study the novel electron gun (E-gun) that can be suitable for high power microwave device applications, adopting two forms of discharge channel, 1: a single hole channel, the structure can produce a solid electron beam; 2: porous holes channel, the structure can generate multiple electronic injection which is similar to the annular electron beam.

Tuning charge–discharge induced unit cell breathing in layer-structured cathode materials for lithium-ion batteries

DOE PAGES

Zhou, Yong-Ning; Ma, Jun; Hu, Enyuan; ...

2014-11-18

Through a systematic study of lithium molybdenum trioxide (Li 2MoO 3), a new ‘unit cell breathing’ mechanism is introduced based on both crystal and electronic structural changes of transition metal oxide cathode materials during charge–discharge: For widely used LiMO 2 (M = Co, Ni, Mn), lattice parameters, a and b, contracts during charge. However, for Li 2MoO 3, such changes are in opposite directions. Metal–metal bonding is used to explain such ‘abnormal’ behaviour and a generalized hypothesis is developed. The expansion of M–M bond becomes the controlling factor for a(b) evolution during charge, in contrast to the shrinking M–O asmore » controlling factor in ‘normal’ materials. The cation mixing caused by migration of Mo ions at higher oxidation state provides the benefits of reducing the c expansion range in early stage of charging and suppressing the structure collapse at high voltage charge. These results open a new strategy for designing and engineering layered cathode materials for high energy density lithium-ion batteries.« less

Effect of cathode material on the electrorefining of U in LiCl-KCl molten salts

NASA Astrophysics Data System (ADS)

Lee, Chang Hwa; Kim, Tack-Jin; Park, Sungbin; Lee, Sung-Jai; Paek, Seung-Woo; Ahn, Do-Hee; Cho, Sung-Ki

2017-05-01

The influence of cathode materials on the U electrorefining process is examined using electrochemical measurements and SEM-EDX observations. Stainless steel (STS), Mo, and W electrodes exhibit similar U reduction/oxidation behavior in 500 °C LiCl-KCl-UCl3 molten salts, as revealed by the cyclic voltammograms. However, slight shifts are observed in the cathodic and anodic peak potentials at the STS electrode, which are related to the fast reduction/oxidation kinetics associated with this electrode. The U deposits on the Mo and W electrodes consist of uniform dendritic chains of U in rhomboidal-shaped crystals, whereas several U dendrites protruding from the surface are observed for the STS electrode. EDX mapping of the electrode surfaces reveals that simple scraping of the U dendrites from W electrodes pretreated in dilute HCl solutions to dissolve the residual salt, results in clear removal of the U deposits, whereas a thick U deposit layer strongly adheres to the STS electrode surface even after treatment. This result is expected to contribute to the development of an effective and continuous U recovery process using electrorefining.

Multiangular Rod-Shaped Na0.44MnO2 as Cathode Materials with High Rate and Long Life for Sodium-Ion Batteries.

PubMed

Liu, Qiannan; Hu, Zhe; Chen, Mingzhe; Gu, Qinfen; Dou, Yuhai; Sun, Ziqi; Chou, Shulei; Dou, Shi Xue

2017-02-01

The tunnel-structured Na 0.44 MnO 2 is considered as a promising cathode material for sodium-ion batteries because of its unique three-dimensional crystal structure. Multiangular rod-shaped Na 0.44 MnO 2 have been first synthesized via a reverse microemulsion method and investigated as high-rate and long-life cathode materials for Na-ion batteries. The microstructure and composition of prepared Na 0.44 MnO 2 is highly related to the sintering temperature. This structure with suitable size increases the contact area between the material and the electrolyte and guarantees fast sodium-ion diffusion. The rods prepared at 850 °C maintain specific capacity of 72.8 mA h g -1 and capacity retention of 99.6% after 2000 cycles at a high current density of 1000 mA g -1 . The as-designed multiangular Na 0.44 MnO 2 provides new insight into the development of tunnel-type electrode materials and their application in rechargeable sodium-ion batteries.

First-principles investigation of the structural characteristics of LiMO2 cathode materials for lithium secondary batteries

NASA Astrophysics Data System (ADS)

Kim, Yongseon

2015-11-01

The structural features related to the defects of LiMO2 (M = Ni, Co, Mn) cathode materials for lithium secondary batteries were investigated by a simulation of phase diagrams based on first-principle calculations. Crystal models with various types of point defects were designed and dealt with as independent phases, which enabled an examination of the thermodynamic stability of the defects. A perfect phase without defects appeared to be the most stable for LiCoO2, whereas the formation of Li vacancies, O vacancies, and antisites between Li and Ni was thermodynamically unavoidable for LiNiO2. The introduction of both Co and Mn in LiNiO2 was effective in reducing the formation of point defects, but increasing the relative amount of Mn was undesirable because the antisite defect remained stable with Mn doping. The simulation showed good agreement with the experimental data and previous reports. Therefore, the method and the results of this study are expected to be useful for examining the synthesis, structure and related properties of layer-structured cathode materials.

All-tantalum electrolytic capacitor

NASA Technical Reports Server (NTRS)

Green, G. E., Jr.

1977-01-01

Device uses single-compression tantalum-to-tantalum seal. Single-compression seal allows better utilization of volume within device. As result of all-tantalum case and lengthened cathode, electrical parameters, particularly equivalent series resistance and capacitance stability, improved over silver-cased capacitor.

Impedance/thermally stimulated depolarization current and microstructural relations at interfaces in degraded perovskite dielectrics

NASA Astrophysics Data System (ADS)

Liu, Wei-En

In this work, a detailed investigation of electrical degradation has been performed on a model perovskite dielectric, Fe-doped SrTiO3 in both single and polycrystalline forms. In the single crystals, three different types of relaxation process were identified by TSDC, namely dipolar orientation of Fe'Ti-VÖ complexes, trap charges of FexTi-VÖ , and ionic space charge with the mobile VÖ . The energetics and concentrations of these are monitored as a function of the degradation process. Furthermore, IS is used to model the mechanisms that are spatially redistributed owning to the migration of VÖ towards the cathodic region of the crystal. Through modeling all the complex impedance Z*, modulus M*, admittance Y* and capacitance C*, an equivalent circuit model can be developed and key contributors to the IS can be identified. From this it is considered that the cathodic region changes to a conduction mechanism that is both band electron and polaron controlled. The major change during the degradation is to the polaron conduction pathways. Due to the nature of low polaron hopping mobility in this model system, the conductivity from both conductions become comparable providing that the calculated polaron concentration is around 5 order greater than that of band electron. The spatial dimension of the distributed conduction mechanisms is also modeled through the I.S. analysis. Excellent agreement is obtained between the IS data and the EELS data, where ≈30 microm of conducting region is developed at the cathode, and a corresponding high oxygen vacancy concentration on the order of 10 19/cm3 is obtained after degradation. Other than those relaxation mechanisms identified in the Fe-doped SrTiO 3 single crystal system, an extra relaxation mechanism was found in the polycrystalline systems and was attributed to the relaxation of oxygen vacancies across grain boundaries. Using the initial rise method of TSDC, the activation energies estimated for the relaxation of defect dipoles, the in-grain oxygen vacancies pile up at grain boundaries, and relaxation of oxygen vacancies across grain boundaries are 0.73+/-0.03, 0.86+/-0.07, and 1.1+/-0.09 eV, respectively. An ionic demixing model is applied to account for the evolution of TSDC spectra and to explain changes to the leakage behavior of the degraded samples. In the case of the polycrystalline system, it is suggested that a strong degradation to the insulation resistance occurs when oxygen vacancies migrate across grain boundaries and start to pile up at the cathode region of metallic electrodes. Prior to that point, the vacancies accumulate at partial blocking grain boundaries in each of the crystallites. For the TSDC studies in Ni-BaTiO3 MLCCs, besides two pyroelectric peaks released from the ferroelectric core and shell phase regions, an additional two peaks above the core Curie temperature were ascribed to the relaxation of two types of oxygen vacancy motions, in grain and across grain boundary oxygen vacancy transportation. Activation energies calculated for in grain and across grain boundary oxygen vacancy peaks are 1.06+/-0.05 and 1.24+/-0.08 eV, respectively. Another important multi-layer capacitive device is the so-called COG capacitor. In designing COG capacitors, high field break down properties are required at elevated temperatures above 85°C. A source of the electrical breakdown could be the depopulation of trapped charge. Therefore the trapped charge energies and concentrations in COG capacitors were investigated. The capacitor's MnO content was found to strongly influence the trapped charge concentration as measured by TSDC. TSDC to electrolytic capacitors was also demonstrated. It is shown that TSDC technique can be a powerful tool to understand underlying defect properties which are not manifested in traditional electrical measurements such as I-V measurement. Electrolytic capacitors based on tantalum oxide are often limited in their performance at high fields and high temperatures due to trapped charges. It is known that leakage is often controlled by Poole-Frankel conduction mechanisms in Ta2O5 electrolytic capacitors. It is determined through I-V measurements that the leakage current indeed follows the Poole-Frenkel conduction characteristic under high field. A parallel TSDC study also confirms at high field and high temperature trapped charge phenomenon. Through the use of TSDC, a new high voltage Poole--Frenkel mechanism at highest field range, >64V, in this study was discovered. It is concluded that TSDC is one of best techniques for capacitor characterization, and recommended other TSDC methods that could be extended to enhance our understanding of structure-property-processing relations in capacitor characterization. (Abstract shortened by UMI.)

Onsite-effects of dual-hemisphere versus conventional single-hemisphere transcranial direct current stimulation: A functional MRI study.

PubMed

Kwon, Yong Hyun; Jang, Sung Ho

2012-08-25

We performed functional MRI examinations in six right-handed healthy subjects. During functional MRI scanning, transcranial direct current stimulation was delivered with the anode over the right primary sensorimotor cortex and the cathode over the left primary sensorimotor cortex using dual-hemispheric transcranial direct current stimulation. This was compared to a cathode over the left supraorbital area using conventional single-hemispheric transcranial direct current stimulation. Voxel counts and blood oxygenation level-dependent signal intensities in the right primary sensorimotor cortex regions were estimated and compared between the two transcranial direct current stimulation conditions. Our results showed that dual-hemispheric transcranial direct current stimulation induced greater cortical activities than single-hemispheric transcranial direct current stimulation. These findings suggest that dual-hemispheric transcranial direct current stimulation may provide more effective cortical stimulation than single-hemispheric transcranial direct current stimulation.

Onsite-effects of dual-hemisphere versus conventional single-hemisphere transcranial direct current stimulation

PubMed Central

Kwon, Yong Hyun; Jang, Sung Ho

2012-01-01

We performed functional MRI examinations in six right-handed healthy subjects. During functional MRI scanning, transcranial direct current stimulation was delivered with the anode over the right primary sensorimotor cortex and the cathode over the left primary sensorimotor cortex using dual-hemispheric transcranial direct current stimulation. This was compared to a cathode over the left supraorbital area using conventional single-hemispheric transcranial direct current stimulation. Voxel counts and blood oxygenation level-dependent signal intensities in the right primary sensorimotor cortex regions were estimated and compared between the two transcranial direct current stimulation conditions. Our results showed that dual-hemispheric transcranial direct current stimulation induced greater cortical activities than single-hemispheric transcranial direct current stimulation. These findings suggest that dual-hemispheric transcranial direct current stimulation may provide more effective cortical stimulation than single-hemispheric transcranial direct current stimulation. PMID:25624815

Novel microbial fuel cell design to operate with different wastewaters simultaneously.

PubMed

Mathuriya, Abhilasha Singh

2016-04-01

A novel single cathode chamber and multiple anode chamber microbial fuel cell design (MAC-MFC) was developed by incorporating multiple anode chambers into a single unit and its performance was checked. During 60 days of operation, performance of MAC-MFC was assessed and compared with standard single anode/cathode chamber microbial fuel cell (SC-MFC). The tests showed that MAC-MFC generated stable and higher power outputs compared with SC-MFC and each anode chamber contributed efficiently. Further, MAC-MFCs were incorporated with different wastewaters in different anode chambers and their behavior in MFC performance was observed. MAC-MFC efficiently treated multiple wastewaters simultaneously at low cost and small space, which claims its candidature for future possible scale-up applications. Copyright © 2015. Published by Elsevier B.V.

Crucibleless crystal growth and Radioluminescence study of calcium tungstate single crystal fiber

NASA Astrophysics Data System (ADS)

Silva, M. S.; Jesus, L. M.; Barbosa, L. B.; Ardila, D. R.; Andreeta, J. P.; Silva, R. S.

2014-11-01

In this article, single phase and high optical quality scheelite calcium tungstate single crystal fibers were grown by using the crucibleless laser heated pedestal growth technique. The as-synthesized calcium tungstate powders used for shaping seed and feed rods were investigated by X-ray diffraction technique. As-grown crystals were studied by Raman spectroscopy and Radioluminescence measurements. The results indicate that in both two cases, calcined powder and single crystal fiber, only the expected scheelite CaWO4 phase was observed. It was verified large homogeneity in the crystal composition, without the presence of secondary phases. The Radioluminescence spectra of the as-grown single crystal fibers are in agreement with that present in Literature for bulk single crystals, presented a single emission band centered at 420 nm when irradiated with β-rays.

Single crystalline growth of a soluble organic semiconductor in a parallel aligned liquid crystal solvent using rubbing-treated polyimide films

NASA Astrophysics Data System (ADS)

Matsuzaki, Tomoya; Shibata, Yosei; Takeda, Risa; Ishinabe, Takahiro; Fujikake, Hideo

2017-01-01

For directional control of organic single crystals, we propose a crystal growth method using liquid crystal as the solvent. In this study, we examined the formation of 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) single crystals using a parallel aligned liquid crystal (LC) cell and rubbing-treated polyimide films in order to clarify the effects of LC alignment on anisotropic C8-BTBT crystal growth. Based on the results, we found that the crystal growth direction of C8-BTBT single crystals was related to the direction of the aligned LC molecules because of rubbing treatment. Moreover, by optical evaluation, we found that the C8-BTBT single crystals have a aligned molecular structure.

Revealing mechanism responsible for structural reversibility of single-crystal VO 2 nanorods upon lithiation/delithiation

DOE PAGES

Liu, Qi; Tan, Guoqiang; Wang, Peng; ...

2017-04-17

A pure phase of VO 2(B) nanorods have been synthesized through an energy-efficient microwave hydrothermal reaction and used as cathode materials of lithium ion batteries, which exhibit promising specific capacity (e.g., 130 mA h g -1 even after 100 charge/discharge cycles) and rate capacity (e.g., ~130 mA h g -1 at a high current of 400 mA g -1). The excellent cyclability originates from the structural reversibility of VO 2(B) upon lithiation/delithiation that is confirmed by the in situ high-energy synchrotron X-ray diffraction (HEXRD) and in situ x-ray adsorption near-edge spectroscopy (XANES) of the VO 2 nanorods in operating batterymore » cells. As a result, the real-time results reveal that discharge forces lithium ions to insert firstly into the tunnels with the largest size along b direction followed by the second largest tunnels along c direction, which is completely reversible in the charge process.« less

Photovoltaic solar energy conversion in the '80s

NASA Astrophysics Data System (ADS)

Chevalier, I.

1981-04-01

The potential for photovoltaic solar energy conversion in the generation of electricity to meet the needs of industrial and developing nations in the 1980s is discussed. The current technology of photovoltaic cells and modules, which are for the most part based on single crystal silicon and can deliver peak powers of 2 to 40 W at 6 to 12 V, is reviewed and prospects for cost reduction in the short- and medium-term by the development of new materials and production methods and increased cell efficiency and in the long term by the development of thin film cells, alternative compounds and mass production are indicated. Possible applications of photovoltaic-derived electricity are pointed out, including educational television receivers, rural telephones, refrigerators, water pumping and hospitals in developing nations and telecommunications, cathodic protection, signaling, telemetry and low-power pumping applications in industrial nations. Predictions of a photovoltaic peak Watt installed costing less than 10 francs by 1990 and a market above 100 MW in 1985 are pointed out.

Revealing mechanism responsible for structural reversibility of single-crystal VO 2 nanorods upon lithiation/delithiation

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

Liu, Qi; Tan, Guoqiang; Wang, Peng

A pure phase of VO 2(B) nanorods have been synthesized through an energy-efficient microwave hydrothermal reaction and used as cathode materials of lithium ion batteries, which exhibit promising specific capacity (e.g., 130 mA h g -1 even after 100 charge/discharge cycles) and rate capacity (e.g., ~130 mA h g -1 at a high current of 400 mA g -1). The excellent cyclability originates from the structural reversibility of VO 2(B) upon lithiation/delithiation that is confirmed by the in situ high-energy synchrotron X-ray diffraction (HEXRD) and in situ x-ray adsorption near-edge spectroscopy (XANES) of the VO 2 nanorods in operating batterymore » cells. As a result, the real-time results reveal that discharge forces lithium ions to insert firstly into the tunnels with the largest size along b direction followed by the second largest tunnels along c direction, which is completely reversible in the charge process.« less

Study on AN Intermediate Temperature Planar Sofc

NASA Astrophysics Data System (ADS)

Wang, Shaorong; Cao, Jiadi; Chen, Wenxia; Lu, Zhiyi; Wang, Daqian; Wen, Ting-Lian

An ITSOFC consisted of Ni/YSZ anode supported YSZ composite thin film and La0.6Sr0.4CoO3 (LSCO) cathode combined with a Ce0.8Sm0.2O1.9 (CSO) interlayer was studied. Tape cast method was applied to prepare green sheets of Ni/YSZ anode supported YSZ composite thin film. After isostatic pressing and cosintering, the YSZ film on the Ni/YSZ anode was gas-tight dense, and 15-30μm thick. The area of the composite film was over 100 cm2. A CSO interlayer was sintered on to the YSZ electrolyte film to protect LSCO cathode from reaction with YSZ at high temperatures. The LSCO cathode layer was screen printed onto the CSO interlayer and sintered at 1200°C for 3h to form a single cell. The obtained single cell was operated with H2 as fuel and O2 as oxidant. The cell performance and impedance were measured and discussed relating with the component contributions.

Investigation of the Li–S Battery Mechanism by Real-Time Monitoring of the Changes of Sulfur and Polysulfide Species during the Discharge and Charge

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

Zheng, Dong; Liu, Dan; Harris, Joshua B.

The mechanism of the sulfur cathode in Li-S batteries has been proposed. It was revealed by the real-time quantitative determination of polysulfide species and elemental sulfur by means of the high performance liquid chromatography in the course of the discharge and recharge of a Li-S battery. A three-step reduction mechanism including two chemical equilibrium reactions was proposed for the sulfur cathode discharge. The typical two-plateau discharge curve for sulfur cathode can be explained. A two-step oxidation mechanism for the Li 2S and Li 2S 2 with a single chemical equilibrium among soluble polysulfide ions was proposed. In conclusion, the chemicalmore » equilibrium among S 5 2-, S 6 2-, S 7 2- and S 8 2- throughout the entire oxidation process resulted for the single flat recharge curve in Li-S batteries.« less

Investigation of the Li–S Battery Mechanism by Real-Time Monitoring of the Changes of Sulfur and Polysulfide Species during the Discharge and Charge

DOE PAGES

Zheng, Dong; Liu, Dan; Harris, Joshua B.; ...

2016-09-09

The mechanism of the sulfur cathode in Li-S batteries has been proposed. It was revealed by the real-time quantitative determination of polysulfide species and elemental sulfur by means of the high performance liquid chromatography in the course of the discharge and recharge of a Li-S battery. A three-step reduction mechanism including two chemical equilibrium reactions was proposed for the sulfur cathode discharge. The typical two-plateau discharge curve for sulfur cathode can be explained. A two-step oxidation mechanism for the Li 2S and Li 2S 2 with a single chemical equilibrium among soluble polysulfide ions was proposed. In conclusion, the chemicalmore » equilibrium among S 5 2-, S 6 2-, S 7 2- and S 8 2- throughout the entire oxidation process resulted for the single flat recharge curve in Li-S batteries.« less

Facile molten salt synthesis of Li2NiTiO4 cathode material for Li-ion batteries.

PubMed

Wang, Yanming; Wang, Yajing; Wang, Fei

2014-01-01

Well-crystallized Li2NiTiO4 nanoparticles are rapidly synthesized by a molten salt method using a mixture of NaCl and KCl salts. X-ray diffraction pattern and scanning electron microscopic image show that Li2NiTiO4 has a cubic rock salt structure with an average particle size of ca. 50 nm. Conductive carbon-coated Li2NiTiO4 is obtained by a facile ball milling method. As a novel 4 V positive cathode material for Li-ion batteries, the Li2NiTiO4/C delivers high discharge capacities of 115 mAh g(-1) at room temperature and 138 mAh g(-1) and 50°C, along with a superior cyclability.

Quantum efficiency temporal response and lifetime of a GaAs cathode in SRF electron gun

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

Wang, E.; Ben-Zvi, I.; Kewisch, J.

2010-05-23

RF electron guns with a strained super lattice GaAs cathode can generate polarized electron beam of higher brightness and lower emittance than do DC guns, due to their higher field gradient at the cathode's surface. In a normal conducting RF gun, the extremely high vaccum required by these cathodes can not be met. We report on an experiment with a superconducting SRF gun, which can maintain a vacuum of nearly 10-12 torr because of cryo-pumping at the temperature of 4.2K. With conventional activation, we obtained a QE of 3% at 532 nm, with lifetime of nearly 3 days in themore » preparation chamber. We plan to use this cathode in a 1.3 GHz 1/2 cell SRF gun to study its performance. In addition, we studied the multipacting at the location of cathode. A new model based on the Forkker-Planck equation which can estimate the bunch length of the electron beam is discussed in this paper. Future particle accelerators such as eRHIC and ILC require high brightness, high current polarized electrons Recently, using a superlattice crystal, the maximum polarization of 95% was reached. Activation with Cs,O lowers the electron affinity and makes it energetically possible for all the electrons excited in to the conduction band and reach the surface to escape into the vacuum. Presently the polarized electron sources are based on DC gun, such as that at the CEBAF at Jlab. In these devices, the life time of the cathode is extended due to the reduced back bombardment in their UHV conditions. However, the low accelerating gradient of the DC guns lead to poor longitudinal emittance. The higher accelerating gradient of the RF gun generates low emittance beams. Superconducting RF guns combine the excellent vacuum conditions of the DC guns with the higher accelerating gradients of the RF guns and provide potentially a long lived cathode with very low transverse and longitudinal emittance. In our work at BNL, we successfully activated the GaAs. The quantum efficient is 3% at 532 nm and is expected to improve further. In addition, we studied the multipacting at the location of cathode. A new model based on the Forkker-Planck equation which can estimate the bunch length of the electron beam is discussed in this paper.« less

Ignition and growth modeling of detonation reaction zone experiments on single crystals of PETN and HMX

NASA Astrophysics Data System (ADS)

White, Bradley W.; Tarver, Craig M.

2017-01-01

It has long been known that detonating single crystals of solid explosives have much larger failure diameters than those of heterogeneous charges of the same explosive pressed or cast to 98 - 99% theoretical maximum density (TMD). In 1957, Holland et al. demonstrated that PETN single crystals have failure diameters of about 8 mm, whereas heterogeneous PETN charges have failure diameters of less than 0.5 mm. Recently, Fedorov et al. quantitatively determined nanosecond time resolved detonation reaction zone profiles of single crystals of PETN and HMX by measuring the interface particle velocity histories of the detonating crystals and LiF windows using a PDV system. The measured reaction zone time durations for PETN and HMX single crystal detonations were approximately 100 and 260 nanoseconds, respectively. These experiments provided the necessary data to develop Ignition and Growth (I&G) reactive flow model parameters for the single crystal detonation reaction zones. Using these parameters, the calculated unconfined failure diameter of a PETN single crystal was 7.5 +/- 0.5 mm, close to the 8 mm experimental value. The calculated failure diameter of an unconfined HMX single crystal was 15 +/- 1 mm. The unconfined failure diameter of an HMX single crystal has not yet been determined precisely, but Fedorov et al. detonated 14 mm diameter crystals confined by detonating a HMX-based plastic bonded explosive (PBX) without initially overdriving the HMX crystals.

Emission efficiency optimization of RE 2O 3 doped molybdenum thermionic cathode by application of pattern recognition method

NASA Astrophysics Data System (ADS)

Wang, Jinshu; Liu, Wei; Liu, Yanqin; Zhou, Meiling

2005-09-01

As an alternative for thoriated tungsten thermionic cathodes, molybdenum doped with either a single rare earth oxide such as La 2O 3, Y 2O 3 and Sc 2O 3 or a mixture thereof has been produced by powder metallurgy. It is shown that carbonization can greatly improve the emission properties (i.e. emission capability and stability) of RE 2O 3 doped molybdenum due to the formation of a (metallic) rare earth atomic layer on the surface of the cathode by the reduction reaction of molybdenum carbide and rare earth oxide. Among all the carbonized samples, La 2O 3 and Y 2O 3 co-doped molybdenum cathode showed the best performance in emission. In addition, computer pattern recognition technique has been used to optimize the composition of the material and of the cathode preparation technique. We derive the equation of the emission efficiency as a function of cathode composition and carbonization degree. Based on the projecting coordinates obtained from the equation, the optimum projection region was identified, which can serve as guide for the composition and carbonization degree design.

Degradation Study by Start-Up/Shut-Down Cycling of Superhydrophobic Electrosprayed Catalyst Layers Using a Localized Reference Electrode Technique.

PubMed

Ferreira-Aparicio, Paloma; Chaparro, Antonio M; Folgado, M Antonia; Conde, Julio J; Brightman, Edward; Hinds, Gareth

2017-03-29

Degradation of a polymer electrolyte membrane fuel cell (PEMFC) with electrosprayed cathode catalyst layers is investigated during cyclic start-up and shut-down events. The study is carried out within a single cell incorporating an array of reference electrodes that enables measurement of cell current as a function of local cathode potential (localized polarization curves). Accelerated degradation of the cell by start-up/shut-down cycling gives rise to inhomogeneous performance loss, which is more severe close to the gas outlet and occurs predominantly during start-up. The degradation consists primarily of loss of cathode catalyst activity and increase in cell internal resistance, which is attributed to carbon corrosion and Pt aggregation in both anode and cathode. Cells with an electrosprayed cathode catalyst layer show lower degradation rates during the first 100 cycles, compared with those of a conventional gas diffusion electrode. This difference in behavior is attributed to the high hydrophobicity of the electrosprayed catalyst layer microstructure, which retards the kinetics of corrosion of the carbon support. In the long term, however, the degradation rate is dominated by the Pt/C ratio in the cathode catalyst layer.

High Power Microwaves for Defense and Accelerator Applications

DTIC Science & Technology

1990-06-11

pulsed power machines are typically made for laboratory simulation of charged particle and radiation spectra of nuclear explosions . Early on, it was...cathode and then explosive 10 ionization. After the first few nanoseconds, the electron emission is from a plasma produced at the cathode. Typically the...Virtually nothing is needed except an electron beam source. This power and simplicity makes vircators particularly interesting for single shot or explosively

Removal of ammonium ion from produced waters in petroleum offshore exploitation by a batch single-stage electrolytic process.

PubMed

de Lima, Rosilda Maria Gomes; da Silva Wildhagen, Glória Regina; da Cunha, José Waldemar Silva Dias; Afonso, Julio Carlos

2009-01-30

This work describes a batch single-stage electrochemical process to remove quantitatively the ammonium ion from produced waters from petroleum exploration of the Campos' Basin, seeking to fulfil the directories of the National Brazilian Environmental Council. The anode was made out of titanium covered by a layer of RuO(2)+TiO(2) oxides (Dimensionally Stable Anode), whereas the cathode was made out of pure titanium. Anodic and cathodic compartments were separated by a membrane. The applied current varied from 0.3 to 1.5A. As the current increased NH(4)(+) removal was faster and pH was rapidly decreased to 3. The pH of the anodic compartment increased to approximately 10. When the current was 0.92 A chlorine evolution was observed after 40 min or only 15 min when that current was 1.50 A. In this voltage a deposit containing alkali-earth metal hydroxides/sulphates was formed on the membrane surface of the cathode side, thus suggesting a diffusion process from the anodic to the cathodic compartment. The maximum current applied to the cell must not exceed approximately 0.70 A in order to avoid chlorine evolution. Ammonia removal was over 99.9 wt% at 0.68 A in about 75 min.

Investigation of Ruthenium Dissolution in Advanced Membrane Electrode Assemblies for Direct Methanol Based Fuel Cell Stacks

NASA Technical Reports Server (NTRS)

Valdez, Thomas I.; Firdosy, S.; Koel, B. E.; Narayanan, S. R.

2005-01-01

Dissolution of ruthenium was observed in the 80-cell stack. Duration testing was performed in single cell MEAs to determine the pathway of cell degradation. EDAX analysis on each of the single cell MEAs has shown that the Johnson Matthey commercial catalyst is stable in DMFC operation for 250 hours, no ruthenium dissolution was observed. Changes in the hydrophobicity of the cathode backing papers was minimum. Electrode polarization analysis revealed that the MEA performance loss is attributed to changes in the cathode catalyst layer. Ruthenium migration does not seem to occur during cell operation but can occur when methanol is absent from the anode compartment, the cathode compartment has access to air, and the cells in the stack are electrically connected to a load (Shunt Currents). The open-to-air cathode stack design allowed for: a) The MEAs to have continual access to oxygen; and b) The stack to sustain shunt currents. Ruthenium dissolution in a DMFC stack can be prevented by: a) Developing an internally manifolded stacks that seal reactant compartments when not in operation; b) Bringing the cell voltages to zero quickly when not in operation; and c) Limiting the total number of cells to 25 in an effort to limit shunt currents.

Secondary orientation effects in a single crystal superalloy under mechanical and thermal loads

NASA Technical Reports Server (NTRS)

Kalluri, Sreeramesh; Abdul-Aziz, Ali; Mcgaw, Michael A.

1991-01-01

The nickel-base single crystal superalloy PWA 1480 is a candidate blading material for the advanced turbopump development program of the SSME. In order to improve thermal fatigue resistance of the turbine blades, the single crystal superalloy PWA 1480 is grown along the low modulus zone axes (001) crystal orientation by a directional solidification process. Since cubic single crystal materials such as PWA 1480 exhibit anisotropic elastic behavior, the stresses developed within the single crystal superalloy due to mechanical and thermal loads are likely to be affected by the exact orientation of the secondary crystallographic direction with respect to the geometry of the turbine blade. The effects of secondary crystal orientation on the elastic response of single crystal PWA 1480 superalloy were investigated.

Piezoelectric single crystals for ultrasonic transducers in biomedical applications

PubMed Central

Zhou, Qifa; Lam, Kwok Ho; Zheng, Hairong; Qiu, Weibao; Shung, K. Kirk

2014-01-01

Piezoelectric single crystals, which have excellent piezoelectric properties, have extensively been employed for various sensors and actuators applications. In this paper, the state–of–art in piezoelectric single crystals for ultrasonic transducer applications is reviewed. Firstly, the basic principles and design considerations of piezoelectric ultrasonic transducers will be addressed. Then, the popular piezoelectric single crystals used for ultrasonic transducer applications, including LiNbO3 (LN), PMN–PT and PIN–PMN–PT, will be introduced. After describing the preparation and performance of the single crystals, the recent development of both the single–element and array transducers fabricated using the single crystals will be presented. Finally, various biomedical applications including eye imaging, intravascular imaging, blood flow measurement, photoacoustic imaging, and microbeam applications of the single crystal transducers will be discussed. PMID:25386032

Electrodeposition of Refractory Carbide Coatings.

DTIC Science & Technology

1982-12-30

refractory carbide coatings from molten salts is described. It consists of the simultaneous reduction of the appropriate metal species dissolved in the...Electrodeposition Molden salts 20. ASSTRACT (Continue an reve.e. 0g.. It necooom wed identify bp block nu.be) A novel method for electrodepositing...respectively. Electrolysis resulted in the formation of millimeter-size crystals on the walls of the graphite crucible which served as the cathode. Analysis of

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

Preparation of a Non-Polar ZnO Film on a Single-Crystal NdGaO3 Substrate by the RF Sputtering Method

NASA Astrophysics Data System (ADS)

Kashiwaba, Y.; Tanaka, Y.; Sakuma, M.; Abe, T.; Imai, Y.; Kawasaki, K.; Nakagawa, A.; Niikura, I.; Kashiwaba, Y.; Osada, H.

2018-04-01

Preparation of non-polar ZnO ( 11\\overline{2} 0 ) films on single-crystal NdGaO3 (NGO) (001) substrates was successfully achieved by the radio frequency (RF) sputtering method. Orientation, deposition rate, and surface roughness of ZnO films strongly depend on the working pressure. Characteristics of ZnO films deposited on single-crystal NGO (001) substrates were compared with those of ZnO films deposited on single-crystal sapphire ( 01\\overline{1} 2 ) substrates. An x-ray diffraction peak of the ZnO ( 11\\overline{2} 0 ) plane was observed on ZnO films deposited on single-crystal NGO (001) substrates under working pressure of less than 0.5 Pa. On the other hand, uniaxially oriented ZnO ( 11\\overline{2} 0 ) films on single-crystal sapphire ( 01\\overline{1} 2 ) substrates were observed under working pressure of 0.1 Pa. The mechanism by which the diffraction angle of the ZnO ( 11\\overline{2} 0 ) plane on single-crystal NGO (001) substrates was shifted is discussed on the basis of anisotropic stress of lattice mismatch. The deposition rate of ZnO films decreased with an increase in working pressure, and the deposition rate on single-crystal NGO (001) substrates was larger than that on single-crystal sapphire ( 01\\overline{1} 2 ) substrates. Root mean square (RMS) roughness of ZnO films increased with an increase in working pressure, and RMS roughness of ZnO films on single-crystal NGO (001) substrates was smaller than that of ZnO films on single-crystal sapphire ( 01\\overline{1} 2 ) substrates even though the film thickness on single-crystal NGO (001) substrates was greater than that on sapphire substrates. It is thought that a single-crystal NGO (001) substrate is useful for deposition of non-polar ZnO ( 11\\overline{2} 0 ) films.

Electrical characteristics of organic perylene single-crystal-based field-effect transistors

NASA Astrophysics Data System (ADS)

Lee, Jin-Woo; Kang, Han-Saem; Kim, Min-Ki; Kim, Kihyun; Cho, Mi-Yeon; Kwon, Young-Wan; Joo, Jinsoo; Kim, Jae-Il; Hong, Chang-Seop

2007-12-01

We report on the fabrication of organic field-effect transistors (OFETs) using perylene single crystal as the active material and their electrical characteristics. Perylene single crystals were directly grown from perylene powder in a furnace using a relatively short growth time of 1-3 h. The crystalline structure of the perylene single crystals was characterized by means of a single-crystal x-ray diffractometer. In order to place the perylene single crystal onto the Au electrodes of the field-effect transistor, a polymethlymethacrylate thin layer was spin-coated on top of the crystal surface. The OFETs fabricated using the perylene single crystal showed a typical p-type operating mode. The field-effect mobility of the perylene crystal based OFETs was measured to be ˜9.62×10-4 cm2/V s at room temperature. The anisotropy of the mobility implying the existence of different mobilities when applying currents in different directions was observed for the OFETs, and the existence of traps in the perylene crystal was found through the measurements of the temperature-dependent mobility at various operating drain voltages.

Exploring the folding pattern of a polymer chain in a single crystal by combining single-molecule force spectroscopy and steered molecular dynamics simulations.

PubMed

Song, Yu; Feng, Wei; Liu, Kai; Yang, Peng; Zhang, Wenke; Zhang, Xi

2013-03-26

Understanding the folding pattern of a single polymer chain within its single crystal will shed light on the mechanism of crystallization. Here, we use the combined techniques of atomic force microscopy (AFM)-based single-molecule force spectroscopy (SMFS) and steered molecular dynamics (SMD) simulations to study the folding pattern of a polyethylene oxide (PEO) chain in its single crystal. Our results show that the folding pattern of a PEO chain in the crystal formed in dilute solution follows the adjacent re-entry folding model. While in the crystal obtained from the melt, the nonadjacent folding with large and irregular loops contributes to big force fluctuations in the force-extension curves. The method established here can offer a novel strategy to directly unravel the chain-folding pattern of polymer single crystals at single-molecule level.

Effect of amaranth dye on the growth and properties of conventional and SR method grown KAP single crystals

NASA Astrophysics Data System (ADS)

Babu Rao, G.; P., Rajesh; Ramasamy, P.

2018-04-01

The 0.1 mol% amaranth added KAP single crystals were grown from aqueous solutions by both slow evaporation solution technique and Sankaranarayanan-Ramasamy method. The single crystal having dimension of 45 mm length and 12 mm diameter was grown with growth rate of 1.5 mm/day using SR method. 87 % transmittance is obtained for SR method grown amaranth added KAP single crystal. The high intense luminescence at 661 nm is obtained from amaranth added conventional and SR method grown KAP single crystal. The amaranth added KAP single crystal possesses good mechanical and laser damage threshold stability.

Capacity fade of LiNi(1-x-y)CoxAlyO2 cathode for lithium-ion batteries during accelerated calendar and cycle life test. I. Comparison analysis between LiNi(1-x-y)CoxAlyO2 and LiCoO2 cathodes in cylindrical lithium-ion cells during long term storage test

NASA Astrophysics Data System (ADS)

Watanabe, Shoichiro; Kinoshita, Masahiro; Nakura, Kensuke

2014-02-01

Ni-based LiNi(1-x-y)CoxAlyO2 (NCA) and LiCoO2 (LCO) cathode materials taken out of lithium-ion cells after storage for 2 years at 45 °C were analyzed by various spectroscopic techniques. X-ray photoelectron spectroscopy exhibited that there was no difference between NCA and LCO. On the other hand, scanning transmission electron microscopy-electron energy-loss spectroscopy demonstrated there was a remarkably large difference between the two cathode materials. Ni-L2,3 energy-loss near-edge structure (ELNES) spectra of the NCA showed a peak at about 856.5 eV, which was assigned to trivalent nickel, was maintained even after storage, indicating that the NCA had no significant change in its surface structure during storage. On the other hand, in the Co-L2,3 ELNES spectra of the LCO a peak at about 782.5 eV, which was assigned to trivalent cobalt, significantly shifted to the lower energies after storage. These results suggest that crystal structure change of the active material surface is a predominant reason of deterioration during the storage test.

Building an Electronic Bridge via Ag Decoration To Enhance Kinetics of Iron Fluoride Cathode in Lithium-Ion Batteries.

PubMed

Li, Yu; Zhou, Xingzhen; Bai, Ying; Chen, Guanghai; Wang, Zhaohua; Li, Hui; Wu, Feng; Wu, Chuan

2017-06-14

As a typical multielectron cathode material for lithium-ion batteries, iron fluoride (FeF 3 ) and its analogues suffer from poor electronic conductivity and low actual specific capacity. Herein, we introduce Ag nanoparticles by silver mirror reaction into the FeF 3 ·0.33H 2 O cathode to build the electronic bridge between the solid (active materials) and liquid (electrolyte) interface. The crystal structures of as-prepared samples are characterized by X-ray diffraction and Rietveld refinement. Moreover, the density of states of FeF 3 ·0.33H 2 O and FeF 3 ·0.33H 2 O/Ag (Ag-decorated FeF 3 ·0.33H 2 O) samples are calculated using the first principle density functional theory. The FeF 3 ·0.33H 2 O/Ag cathodes exhibit significant enhancements on the electrochemical performance in terms of the cycle performance and rate capability, especially for the Ag-decorated amount of 5%. It achieves an initial capacity of 168.2 mA h g -1 and retains a discharge capacity of 128.4 mA h g -1 after 50 cycles in the voltage range of 2.0-4.5 V. It demonstrates that Ag decoration can reduce the band gap, improve electronic conductivity, and elevate intercalation/deintercalation kinetics.

LiAl xCo 1- xO 2 as 4 V cathodes for lithium ion batteries

NASA Astrophysics Data System (ADS)

Huang, Haitao; Rao, G. V. Subba; Chowdari, B. V. R.

Nominal LiAl xCo 1- xO 2 with x ranging from 0.1 to 0.3 was prepared by heating mixture of Al(OH) 3, Co 3O 4 and LiOH at 750°C in air. The effect of substitution of non-transition metal, Al, in LiCoO 2 is investigated as a 4 V cathode for lithium ion. X-ray diffraction (XRD) indicates formation of a single phase (R3¯m) within this range of substitution. When cycled between 4.5 and 2.5 V vs. Li/Li + at a current density of 1 mA cm -2, the LiAl 0.15Co 0.85O 2 cathode exhibits reversible capacity of 160 mA h g -1 initially. XRD of the cathode made at the end of 10 cycles reveals no significant change on host structure.

Er0.4Bi1.6O3-δ - La0.8Sr0.2MnO3-δ nano-composite as a low-temperature firing cathode of solid oxide fuel cell

NASA Astrophysics Data System (ADS)

Kim, Sun Jae; Dayaghi, Amir Masoud; Kim, Kun Joong; Choi, Gyeong Man

2017-03-01

Er0.4Bi1.6O3-δ (ESB) composited with La0.8Sr0.2MnO3-δ (LSM) (2:3 or 3:2 wt:wt) with a bonding aid to decrease firing temperature TF are screen-printed on symmetric single cells composed of a Gd0.2Ce0.8O2-δ (GDC) interlayer/yttria-stabilized zirconia (YSZ) electrolyte/GDC interlayer, and their impedance spectra are compared. Addition of 5 wt % CuO to ESB-LSM (3:2 wt:wt) decreases the cathode TF to 650 °C without increasing cathodic polarization resistance (Rp ∼0.19 Ω cm2 at 650 °C). This ESB-LSM composite can be used as a cathode that can be fired at low temperature.

Solid oxide fuel cell having monolithic cross flow core and manifolding

DOEpatents

Poeppel, Roger B.; Dusek, Joseph T.

1984-01-01

This invention discloses a monolithic core construction having the flow passageways for the fuel and for the oxidant gases extended transverse to one another, whereby full face core manifolding can be achieved for these gases and their reaction products. The core construction provides that only anode material surround each fuel passageway and only cathode material surround each oxidant passageway, each anode and each cathode further sandwiching at spaced opposing sides electrolyte and interconnect materials to define electrolyte and interconnect walls. Webs of the cathode and anode material hold the electrolyte and interconnect walls spaced apart to define the flow passages. The composite anode and cathode wall structures are further alternately stacked on one another (with the separating electrolyte or interconnect material typically being a single common layer) whereby the fuel passageway and the oxidant passageways are disposed transverse to one another.

Solid oxide fuel cell having monolithic cross flow core and manifolding

DOEpatents

Poeppel, R.B.; Dusek, J.T.

1983-10-12

This invention discloses a monolithic core construction having the flow passageways for the fuel and for the oxidant gases extended transverse to one another, whereby full face core manifolding can be achieved for these gases and their reaction products. The core construction provides that only anode material surround each fuel passageway and only cathode material surround each oxidant passageway, each anode and each cathode further sandwiching at spaced opposing sides electrolyte and interconnect materials to define electrolyte and interconnect walls. Webs of the cathode and anode material hold the electrolyte and interconnect walls spaced apart to define the flow passages. The composite anode and cathode wall structures are further alternately stacked on one another (with the separating electrolyte or interconnect material typically being a single common layer) whereby the fuel passageways and the oxidant passageways are disposed transverse to one another.

Partially non-linear stimulation intensity-dependent effects of direct current stimulation on motor cortex excitability in humans.

PubMed

Batsikadze, G; Moliadze, V; Paulus, W; Kuo, M-F; Nitsche, M A

2013-04-01

Transcranial direct current stimulation (tDCS) of the human motor cortex at an intensity of 1 mA with an electrode size of 35 cm(2) has been shown to induce shifts of cortical excitability during and after stimulation. These shifts are polarity-specific with cathodal tDCS resulting in a decrease and anodal stimulation in an increase of cortical excitability. In clinical and cognitive studies, stronger stimulation intensities are used frequently, but their physiological effects on cortical excitability have not yet been explored. Therefore, here we aimed to explore the effects of 2 mA tDCS on cortical excitability. We applied 2 mA anodal or cathodal tDCS for 20 min on the left primary motor cortex of 14 healthy subjects. Cathodal tDCS at 1 mA and sham tDCS for 20 min was administered as control session in nine and eight healthy subjects, respectively. Motor cortical excitability was monitored by transcranial magnetic stimulation (TMS)-elicited motor-evoked potentials (MEPs) from the right first dorsal interosseous muscle. Global corticospinal excitability was explored via single TMS pulse-elicited MEP amplitudes, and motor thresholds. Intracortical effects of stimulation were obtained by cortical silent period (CSP), short latency intracortical inhibition (SICI) and facilitation (ICF), and I wave facilitation. The above-mentioned protocols were recorded both before and immediately after tDCS in randomized order. Additionally, single-pulse MEPs, motor thresholds, SICI and ICF were recorded every 30 min up to 2 h after stimulation end, evening of the same day, next morning, next noon and next evening. Anodal as well as cathodal tDCS at 2 mA resulted in a significant increase of MEP amplitudes, whereas 1 mA cathodal tDCS decreased corticospinal excitability. A significant shift of SICI and ICF towards excitability enhancement after both 2 mA cathodal and anodal tDCS was observed. At 1 mA, cathodal tDCS reduced single-pulse TMS-elicited MEP amplitudes and shifted SICI and ICF towards inhibition. No significant changes were observed in the other protocols. Sham tDCS did not induce significant MEP alterations. These results suggest that an enhancement of tDCS intensity does not necessarily increase efficacy of stimulation, but might also shift the direction of excitability alterations. This should be taken into account for applications of the stimulation technique using different intensities and durations in order to achieve stronger or longer lasting after-effects.

Translation effects on vertical Bridgman growth and optical, mechanical and surface analysis of 2-phenylphenol single crystal

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

Sadhasivam, S., E-mail: sadha.phy1@gmail.com; Perumal, Rajesh Narayana

2-phenylphenol optical crystals were grown in cone ampoules using vertical Bridgman technique. Single crystal of 2-phenylphenol with 150 mm length has been grown. The inclination on the conical part of the ampoule reduces the growth defects in the 2-phenylphenol single crystal. The lattice parameters and structure studied using single crystal X-ray diffraction method. 2-phenylphenol single crystal belongs to orthorhombic space group Fdd2. The micro translation rate affects crystal growth of 2-phenylphenol crystal was studied. The translation rate dependent defects present in the crystal were investigated by transmittance, indentation and etching characterizations. The dislocation induced indentation crack lengths variations were studied. Etchmore » pits and striations observed for the selective etchants furnish significant information on growth aspects and degree of defect present in the crystal.« less

The Use of Laser-Induced Fluorescence to Characterize Discharge Cathode Erosion in a 30 cm Ring-Cusp Ion Thruster

NASA Technical Reports Server (NTRS)

Sovey, James S. (Technical Monitor); Williams, George J., Jr.

2004-01-01

Relative erosion rates and impingement ion production mechanisms have been identified for the discharge cathode of a 30 cm ion engine using laser-induced fluorescence (LIF). Mo and W erosion products as well as neutral and singly ionized xenon were interrogated. The erosion increased with both discharge current and voltage and spatially resolved measurements agreed with observed erosion patters. Ion velocity mapping identified back-flowing ions near the regions of erosion with energies potentially sufficient to generate the level of observed erosion. Ion production regions downstream of the cathode were indicated and were suggested as possible sources of the erosion causing ions.

Silicon/Carbon Anodes with One-Dimensional Pore Structure for Lithium-Ion Batteries

DTIC Science & Technology

2013-08-31

Connected by Single-Wall Carbon Nanotubes for Sodium Ion Battery Cathodes, Nano Letters 12, 5664, 2012. ( § equal contribution)  Chao Luo,§ Yunhua...is superior to that of those conductive additive-incorporated iron oxide anodes, such as amorphous carbon , graphene as well as carbon nanotubes ...electrochemical performance. The C/S composite cathodes were prepared by mixing C/S powders with carbon black and sodium carboxymethyl cellulose (CMC

Highly-flexible fibre battery incorporating polypyrrole cathode and carbon nanotubes anode

NASA Astrophysics Data System (ADS)

Wang, J.; Wang, C. Y.; Too, C. O.; Wallace, G. G.

The development of highly-flexible fibre batteries based on a conducting polymer and single-wall carbon nanotubes (SWNTs) is described. Initially, polypyrrole-hexafluorophosphate (PPy/PF 6) and SWNTs are tested in lithium cells to ascertain their performance. Based on the results, fibre batteries consisting of a PPy/PF 6 cathode and an anode based on SWNTs are fabricated and tested in both a "flooded cell" and 'dry cell', arrangement.

RF Photoelectric injectors using needle cathodes

NASA Astrophysics Data System (ADS)

Lewellen, J. W.; Brau, C. A.

2003-07-01

Photocathode RF guns, in various configurations, are the injectors of choice for both current and future applications requiring high-brightness electron beams. Many of these applications, such as single-pass free-electron lasers, require beams with high brilliance but not necessarily high charge per bunch. Field-enhanced photoelectric emission has demonstrated electron-beam current density as high as 10 10 A/m 2, with a quantum efficiency in the UV that approaches 10% at fields on the order of 10 10 V/m. Thus, the use of even a blunt needle holds promise for increasing cathode quantum efficiency without sacrificing robustness. We present an initial study on the use of needle cathodes in photoinjectors to enhance beam brightness while reducing beam charge. Benefits include lower drive-laser power requirements, easier multibunch operation, lower emittance, and lower beam degradation due to charge-dependent effects in the postinjector accelerator. These benefits result from a combination of a smaller cathode emission area, greatly enhanced RF field strength at the cathode, and the charge scaling of detrimental postinjector linac effects, e.g., transverse wakefields and CSR.

Field Emission Properties of Carbon Nanotube Fibers and Sheets for a High Current Electron Source

NASA Astrophysics Data System (ADS)

Christy, Larry

Field emission (FE) properties of carbon nanotube (CNT) fibers from Rice University and the University of Cambridge have been studied for use within a high current electron source for a directed energy weapon. Upon reviewing the performance of these two prevalent CNT fibers, cathodes were designed with CNT fibers from the University of Cincinnati Nanoworld Laboratory. Cathodes composed of a single CNT fiber, an array of three CNT fibers, and a nonwoven CNT sheet were investigated for FE properties; the goal was to design a cathode with emission current in excess of 10 mA. Once the design phase was complete, the cathode samples were fabricated, characterized, and then analyzed to determine FE properties. Electrical conductivity of the CNT fibers was characterized with a 4-probe technique. FE characteristics were measured in an ultra-high vacuum chamber at Wright-Patterson Air Force Base. The arrayed CNT fiber and the enhanced nonwoven CNT sheet emitter design demonstrated the most promising FE properties. Future work will include further analysis and cathode design using this nonwoven CNT sheet material to increase peak current performance during electron emission.

Ultratough CVD single crystal diamond and three dimensional growth thereof

DOEpatents

Hemley, Russell J [Washington, DC; Mao, Ho-kwang [Washington, DC; Yan, Chih-shiue [Washington, DC

2009-09-29

The invention relates to a single-crystal diamond grown by microwave plasma chemical vapor deposition that has a toughness of at least about 30 MPa m.sup.1/2. The invention also relates to a method of producing a single-crystal diamond with a toughness of at least about 30 MPa m.sup.1/2. The invention further relates to a process for producing a single crystal CVD diamond in three dimensions on a single crystal diamond substrate.

Development of n- and p-type Doped Perovskite Single Crystals Using Solid-State Single Crystal Growth (SSCG) Technique

DTIC Science & Technology

2017-10-09

doped BaTiO3 single crystal) could be also fabricated by using a BaTiO3 ceramics with the same compositional gradient (Fig. 8). This result has...piezoelectric applications. Compositionally PZT ceramics lie near the MPB between the tetragonal and rhombohedral phases and MPB compositions ...single crystal growth) technique are suitable to grow a variety of “n- and p-type doped” perovskite single crystals of complicated compositions . The

Growth of high quality bulk size single crystals of inverted solubility lithium sulphate monohydrate

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

Silambarasan, A.; Rajesh, P., E-mail: rajeshp@ssn.edu.in; Ramasamy, P.

2015-06-24

The paper summarizes the processes of growing large lithium sulfate monohydrate (LSMH) single crystals. We have established a procedure to grow high quality bulk size single crystals of inverted solubility LSMH by a newly developed unidirectional crystallization technique called the Sankeranarayenan - Ramasamy (SR) method. The convective flow of crystal growth processes from solution and the conditions of growing crystals of various aspects were discussed. Good quality LSMH single crystal is grown of the size 20 mmX80 mm without cracks, localized-defects and inclusions. The as-grown crystals are suitable for piezoelectric and nonlinear optical applications.

A new method to evaluate the quality of single crystal Cu by an X-ray diffraction butterfly pattern method

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

Xu Zhenming; Guo Zhenqi; Li Jianguo

2004-12-15

A new method for the evaluation of the quality of an Ohno continuous cast (OCC) Cu single crystal by X-ray diffraction (XRD) butterfly pattern was brought forward. Experimental results show that the growth direction of single crystal Cu is inclined from both sides of the single crystal Cu rod to the axis and is axially symmetric. The degree of deviation from the [100] orientation from the crystal axis is less than 5 deg. with a casting speed 10-40 mm/min. The orientation of single crystal Cu does not have a fixed direction but is in a regular range. Moreover, the orientationmore » of stray grains in the single crystal Cu is random from continuous casting.« less

Spray printing of organic semiconducting single crystals

NASA Astrophysics Data System (ADS)

Rigas, Grigorios-Panagiotis; Payne, Marcia M.; Anthony, John E.; Horton, Peter N.; Castro, Fernando A.; Shkunov, Maxim

2016-11-01

Single-crystal semiconductors have been at the forefront of scientific interest for more than 70 years, serving as the backbone of electronic devices. Inorganic single crystals are typically grown from a melt using time-consuming and energy-intensive processes. Organic semiconductor single crystals, however, can be grown using solution-based methods at room temperature in air, opening up the possibility of large-scale production of inexpensive electronics targeting applications ranging from field-effect transistors and light-emitting diodes to medical X-ray detectors. Here we demonstrate a low-cost, scalable spray-printing process to fabricate high-quality organic single crystals, based on various semiconducting small molecules on virtually any substrate by combining the advantages of antisolvent crystallization and solution shearing. The crystals' size, shape and orientation are controlled by the sheer force generated by the spray droplets' impact onto the antisolvent's surface. This method demonstrates the feasibility of a spray-on single-crystal organic electronics.

Gallium arsenide single crystal solar cell structure and method of making

NASA Technical Reports Server (NTRS)

Stirn, Richard J. (Inventor)

1983-01-01

A production method and structure for a thin-film GaAs crystal for a solar cell on a single-crystal silicon substrate (10) comprising the steps of growing a single-crystal interlayer (12) of material having a closer match in lattice and thermal expansion with single-crystal GaAs than the single-crystal silicon of the substrate, and epitaxially growing a single-crystal film (14) on the interlayer. The material of the interlayer may be germanium or graded germanium-silicon alloy, with low germanium content at the silicon substrate interface, and high germanium content at the upper surface. The surface of the interface layer (12) is annealed for recrystallization by a pulsed beam of energy (laser or electron) prior to growing the interlayer. The solar cell structure may be grown as a single-crystal n.sup.+ /p shallow homojunction film or as a p/n or n/p junction film. A Ga(Al)AS heteroface film may be grown over the GaAs film.

Preparation of fine single crystals of magnetic superconductor RuSr2GdCu2O8-δ by partial melting

NASA Astrophysics Data System (ADS)

Yamaki, Kazuhiro; Bamba, Yoshihiro; Irie, Akinobu

2018-03-01

In this study, fine uniform RuSr2GdCu2O8-δ (RuGd-1212) single crystals have been successfully prepared by partial melting. Synthesis temperature could be lowered to a value not exceeding the decomposition temperature of RuGd-1212 using the Sr-Gd-Cu-O flux. The crystals grown by alumina boats are cubic, which coincides with the result of a previous study of RuGd-1212 single crystals using platinum crucibles. The single crystals were up to 15 × 15 × 15 µm3 in size and their lattice constants were consistent with those of polycrystalline samples reported previously. Although the present size of single crystals is not sufficient for measurements, the partial melting technique will be beneficial for future progress of research using RuGd-1212 single crystals. Appropriate nominal composition, sintering atmosphere, and temperature are essential factors for growing RuGd-1212 single crystals.

Demonstration of single crystal growth via solid-solid transformation of a glass

DOE PAGES

Savytskii, Dmytro; Knorr, Brian; Dierolf, Volkmar; ...

2016-03-18

Many advanced technologies have relied on the availability of single crystals of appropriate material such as silicon for microelectronics or superalloys for turbine blades. Similarly, many promising materials could unleash their full potential if they were available in a single crystal form. However, the current methods are unsuitable for growing single crystals of these oftentimes incongruently melting, unstable or metastable materials. Here we demonstrate a strategy to overcome this hurdle by avoiding the gaseous or liquid phase, and directly converting glass into a single crystal. Specifically, Sb 2S 3 single crystals are grown in Sb-S-I glasses as an example ofmore » this approach. In this first unambiguous demonstration of an all-solid-state glass → crystal transformation, extraneous nucleation is avoided relative to crystal growth via spatially localized laser heating and inclusion of a suitable glass former in the composition. Lastly, the ability to fabricate patterned single-crystal architecture on a glass surface is demonstrated, providing a new class of micro-structured substrate for low cost epitaxial growth, active planar devices, etc.« less

Study of single crystals of metal solid solutions

NASA Technical Reports Server (NTRS)

Doty, J. P.; Reising, J. A.

1973-01-01

The growth of single crystals of relatively high melting point metals such as silver, copper, gold, and their alloys was investigated. The purpose was to develop background information necessary to support a space flight experiment and to generate ground based data for comparison. The ground based data, when compared to the data from space grown crystals, are intended to identify any effects which zero-gravity might have on the basic process of single crystal growth of these metals. The ultimate purposes of the complete investigation are to: (1) determine specific metals and alloys to be investigated; (2) grow single metal crystals in a terrestrial laboratory; (3) determine crystal characteristics, properties, and growth parameters that will be effected by zero-gravity; (4) evaluate terrestrially grown crystals; (5) grow single metal crystals in a space laboratory such as Skylab; (6) evaluate the space grown crystals; (7) compare for zero-gravity effects of crystal characteristics, properties, and parameters; and (8) make a recommendation as to production of these crystals as a routine space manufacturing proceses.

Fast growth with crystal splitting of morphology-controllable Bi2S3 flowers on TiO2 nanotube arrays

NASA Astrophysics Data System (ADS)

Yang, L. X.; Ding, Y. B.; Luo, S. L.; Luo, Y.; Deng, F.; Li, Y.

2013-03-01

Bi2S3 crystals with flower-like morphologies are deposited on TiO2 nanotube arrays (NTs) by applying the cathodic pulse electrodeposition (PED) technique at 120 °C in 20 s. The highly oriented TiO2 NTs/Ti serving as substrate has high surface energy which is favorable for Gibbs free energy decreasing in nucleation process. Numerous boundaries between NTs are nucleation sites for atomic clusters, resulting in a fast nucleation velocity. Effective and fast heterogeneous nucleation initiates a thermodynamic control growth model and finally leads to the fast formation of highly crystallized Bi2S3 with a typical splitting property. Ethylene glycol (EG) was introduced into the electrolytes to inhibit the typical growth along the c axis ([0 0 1] plane) and facilitate the growth along the ab plane, producing Bi2S3 crystals with variable morphologies from sheaves to flowers by increasing EG contents.

Crystal growth and scintillation properties of Pr-doped SrI2 single crystals

NASA Astrophysics Data System (ADS)

Yokota, Yuui; Ito, Tomoki; Yoshino, Masao; Yamaji, Akihiro; Ohashi, Yuji; Kurosawa, Shunsuke; Kamada, Kei; Yoshikawa, Akira

2018-04-01

Pr-doped SrI2 (Pr:SrI2) single crystals with various Pr concentrations were grown by the halide-micro-pulling-down (H-μ-PD) method, and the scintillation properties were investigated. Pr1%:SrI2 single crystal with high transparency could be grown by the H-μ-PD method while Pr2, 3 and 5%:SrI2 single crystals included some cracks and opaque parts. In the photoluminescence spectrum of the Pr1%:SrI2 single crystal, an emission peak originated from the Pr3+ ion was observed around 435 nm while the radioluminescence spectra showed an emission peak around 535 nm for the undoped SrI2 and Pr:SrI2 single crystals. Light yields of Pr1, 2, 3 and 5%:SrI2 single crystals under γ-ray irradiation were 7700, 8700, 7200 and 6700 photons/MeV, respectively. Decay times of Pr1 and 2%:SrI2 single crystals under γ-ray irradiation were 55.9 and 35.0 ns of the fast decay component, and 435 and 408 ns of the slow decay component, respectively.

Ni-P/Zn-Ni compositionally modulated multilayer coatings - Part 1: Electrodeposition and growth mechanism, composition, morphology, roughness and structure

NASA Astrophysics Data System (ADS)

Bahadormanesh, Behrouz; Ghorbani, Mohammad

2018-06-01

The Ni-P/Zn-Ni compositionally modulated multilayer coatings CMMCs were electrodeposited from a single bath by switching the cathodic current density. The composition, surface morphology, roughness, layers growth pattern as well as the phase structure of deposits were extensively studied via SEM, EDS, AFM and XRD analysis. Effects of bath ingredients on the electrodeposition behavior were analyzed through cathodic linear sweep voltammetry. Although the concentration of Zn2+ in bath was 13 times higher than Ni2+, the Zn-Ni deposition potential was much nearer to Ni deposition potential rather than that of Zn. Addition of NaH2PO2 to the Ni deposition bath considerably raised the current density and shifted the crystallization potential of Ni to more nobble values. Codeposition of P with Zn-Ni alloy lead to crack formation in the monolayer that was deposited in 60 mA/cm2. However, the cracks were not observed in the Zn-Ni layers of multilayers. Zn-Ni layers in CMMCs exhibited a three-dimensional pattern of growth while that of Ni-P layers was two-dimensional. Also, the Ni-P deposits tends to fill the discontinuities in Zn-Ni layers and performed leveling properties and lowered the surface roughness of Zn-Ni layers and CMMCs. Structural analysis demonstrated that Ni-P layers were amorphous and the Zn-Ni layers exhibited crystallite phase of Zn11Ni2. Thus, the Ni-P/Zn-Ni CMMCs comprised of alternate layers of amorphous Ni-P and nanocrystalline Zn Ni.

Cationic Intermixing and Reactivity at the La2 Mo2 O9 /La0.8 Sr0.2 MnO3-δ Solid Oxide Fuel Cell Electrolyte-Cathode Interface.

PubMed

Ravella, Uday K; Liu, Jingjing; Corbel, Gwenaël; Skinner, Stephen J; Lacorre, Philippe

2016-08-23

Among standard high-temperature cathode materials for solid oxide fuel cells, La0.8 Sr0.2 MnO3-δ (LSM) displays the least reactivity with the oxide-ion conductor La2 Mo2 O9 (LMO), yet a reaction is observed at high processing temperatures, identified by using XRD and focused ion beam secondary-ion mass spectrometry (FIB-SIMS) after annealing at 1050 and 1150 °C. Additionally, Sr and Mn solutions were deposited and annealed on LMO pellets, as well as a Mo solution on a LSM pellet. From these studies several reaction products were identified by using XRD and located by using FIB-SIMS on the surface of pelletised samples. We used depth profiling to show that the reactivity extended up to ∼10 μm from the surface region. If Sr was present, a SrMoO4 -type scheelite phase was always observed as a reaction product, and if Mn was present, LaMnO3+δ single crystals were observed on the surface of the LMO pellets. Additional phases such as La2 MoO6 and La6 MoO12 were also detected depending on the configuration and annealing temperature. Reaction mechanisms and detailed reaction formulae are proposed to explain these observations. The strongest driving force for cationic diffusion appears to originate from Mo(6+) and Mn(3+) cations, rather than from Sr(2+) . © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Numerical study of slip system activity and crystal lattice rotation under wedge nanoindents in tungsten single crystals

NASA Astrophysics Data System (ADS)

Volz, T.; Schwaiger, R.; Wang, J.; Weygand, S. M.

2018-05-01

Tungsten is a promising material for plasma facing components in future nuclear fusion reactors. In the present work, we numerically investigate the deformation behavior of unirradiated tungsten (a body-centered cubic (bcc) single crystal) underneath nanoindents. A finite element (FE) model is presented to simulate wedge indentation. Crystal plasticity finite element (CPFE) simulations were performed for face-centered and body-centered single crystals accounting for the slip system family {110} <111> in the bcc crystal system and the {111} <110> slip family in the fcc system. The 90° wedge indenter was aligned parallel to the [1 ¯01 ]-direction and indented the crystal in the [0 1 ¯0 ]-direction up to a maximum indentation depth of 2 µm. In both, the fcc and bcc single crystals, the activity of slip systems was investigated and compared. Good agreement with the results from former investigations on fcc single crystals was observed. Furthermore, the in-plane lattice rotation in the material underneath an indent was determined and compared for the fcc and bcc single crystals.

High performance planar p-i-n perovskite solar cells with crown-ether functionalized fullerene and LiF as double cathode buffer layers

NASA Astrophysics Data System (ADS)

Liu, Xiaodong; Lei, Ming; Zhou, Yi; Song, Bo; Li, Yongfang

2015-08-01

Double cathode buffer layers (CBLs) composed of fullerene derivative functionalized with a crown-ether end group in its side chain (denoted as PCBC) and a LiF layer were introduced between the PCBM acceptor layer and the top cathode in planar p-i-n perovskite solar cells (pero-SCs) based on CH3NH3PbI3-XClX. The devices with the PCBC/LiF double CBLs showed significant improvements in power conversion efficiency (PCE) and long-term stability when compared to the device with LiF single CBL. Through optimizing the spin-coating speed of PCBC, a maximum PCE of 15.53% has been achieved, which is approximately 15% higher than that of the device with single LiF CBL. The remarkable improvement in PCE can be attributed to the formation of a better ohmic contact in the CBL between PCBC and LiF/Al electrode arising from the dipole moment of PCBC, leading to the enhanced fill factor and short-circuit current density (Jsc). Besides the PCE, the long-term stability of the devices with PCBC interlayer is also superior to that of the device with LiF single CBL, which is due to the more effective protection for the perovskite/PCBM interface.

A preliminary review of organic materials single crystal growth by the Czochralski technique

NASA Astrophysics Data System (ADS)

Penn, B. G.; Shields, A. W.; Frazier, D. O.

1988-09-01

The growth of single crystals of organic compounds by the Czochralski method is reviewed. From the literature it is found that single crystals of benzil, a nonlinear optical material with a d sub 11 value of 11.2 + or - 1.5 x d sub 11 value of alpha quartz, has fewer dislocations than generally contained in Bridgman crystals. More perfect crystals were grown by repeated Czochralski growth. This consists of etching away the defect-containing portion of a Czochralski grown crystal and using it as a seed for further growth. Other compounds used to grow single crystals are benzophenone, 12-tricosanone (laurone), and salol. The physical properties, growth apparatus, and processing conditions presented in the literature are discussed. Moreover, some of the possible advantages of growing single crystals of organic compounds in microgravity to obtain more perfect crystals than on Earth are reviewed.

A preliminary review of organic materials single crystal growth by the Czochralski technique

NASA Technical Reports Server (NTRS)

Penn, B. G.; Shields, A. W.; Frazier, D. O.

1988-01-01

The growth of single crystals of organic compounds by the Czochralski method is reviewed. From the literature it is found that single crystals of benzil, a nonlinear optical material with a d sub 11 value of 11.2 + or - 1.5 x d sub 11 value of alpha quartz, has fewer dislocations than generally contained in Bridgman crystals. More perfect crystals were grown by repeated Czochralski growth. This consists of etching away the defect-containing portion of a Czochralski grown crystal and using it as a seed for further growth. Other compounds used to grow single crystals are benzophenone, 12-tricosanone (laurone), and salol. The physical properties, growth apparatus, and processing conditions presented in the literature are discussed. Moreover, some of the possible advantages of growing single crystals of organic compounds in microgravity to obtain more perfect crystals than on Earth are reviewed.

Mechanochemical Synthesis of Carbon Nanothread Single Crystals.

PubMed

Li, Xiang; Baldini, Maria; Wang, Tao; Chen, Bo; Xu, En-Shi; Vermilyea, Brian; Crespi, Vincent H; Hoffmann, Roald; Molaison, Jamie J; Tulk, Christopher A; Guthrie, Malcolm; Sinogeikin, Stanislav; Badding, John V

2017-11-15

Synthesis of well-ordered reduced dimensional carbon solids with extended bonding remains a challenge. For example, few single-crystal organic monomers react under topochemical control to produce single-crystal extended solids. We report a mechanochemical synthesis in which slow compression at room temperature under uniaxial stress can convert polycrystalline or single-crystal benzene monomer into single-crystalline packings of carbon nanothreads, a one-dimensional sp 3 carbon nanomaterial. The long-range order over hundreds of microns of these crystals allows them to readily exfoliate into fibers. The mechanochemical reaction produces macroscopic single crystals despite large dimensional changes caused by the formation of multiple strong, covalent C-C bonds to each monomer and a lack of reactant single-crystal order. Therefore, it appears not to follow a topochemical pathway, but rather one guided by uniaxial stress, to which the nanothreads consistently align. Slow-compression room-temperature synthesis may allow diverse molecular monomers to form single-crystalline packings of polymers, threads, and higher dimensional carbon networks.

A new cathode material for super-valent battery based on aluminium ion intercalation and deintercalation

PubMed Central

Wang, Wei; Jiang, Bo; Xiong, Weiyi; Sun, He; Lin, Zheshuai; Hu, Liwen; Tu, Jiguo; Hou, Jungang; Zhu, Hongmin; Jiao, Shuqiang

2013-01-01

Due to their small footprint and flexible siting, rechargeable batteries are attractive for energy storage systems. A super-valent battery based on aluminium ion intercalation and deintercalation is proposed in this work with VO2 as cathode and high-purity Al foil as anode. First-principles calculations are also employed to theoretically investigate the crystal structure change and the insertion-extraction mechanism of Al ions in the super-valent battery. Long cycle life, low cost and good capacity are achieved in this battery system. At the current density of 50 mAg−1, the discharge capacity remains 116 mAhg−1 after 100 cycles. Comparing to monovalent Li-ion battery, the super-valent battery has the potential to deliver more charges and gain higher specific capacity. PMID:24287676

Facile molten salt synthesis of Li2NiTiO4 cathode material for Li-ion batteries

PubMed Central

2014-01-01

Well-crystallized Li2NiTiO4 nanoparticles are rapidly synthesized by a molten salt method using a mixture of NaCl and KCl salts. X-ray diffraction pattern and scanning electron microscopic image show that Li2NiTiO4 has a cubic rock salt structure with an average particle size of ca. 50 nm. Conductive carbon-coated Li2NiTiO4 is obtained by a facile ball milling method. As a novel 4 V positive cathode material for Li-ion batteries, the Li2NiTiO4/C delivers high discharge capacities of 115 mAh g-1 at room temperature and 138 mAh g-1 and 50°C, along with a superior cyclability. PMID:24855459

Raster graphic helmet-mounted display study

NASA Technical Reports Server (NTRS)

Beamon, William S.; Moran, Susanna I.

1990-01-01

A design of a helmet mounted display system is presented, including a design specification and development plan for the selected design approach. The requirements for the helmet mounted display system and a survey of applicable technologies are presented. Three helmet display concepts are then described which utilize lasers, liquid crystal display's (LCD's), and subminiature cathode ray tubes (CRT's), respectively. The laser approach is further developed in a design specification and a development plan.

Aluminum manganese oxides with mixed crystal structure: high-energy-density cathodes for rechargeable sodium batteries.

PubMed

Han, Dong-Wook; Ku, Jun-Hwan; Kim, Ryoung-Hee; Yun, Dong-Jin; Lee, Seok-Soo; Doo, Seok-Gwang

2014-07-01

We report a new discovery for enhancing the energy density of manganese oxide (Nax MnO2 ) cathode materials for sodium rechargeable batteries by incorporation of aluminum. The Al incorporation results in NaAl(0.1) Mn(0.9) O2 with a mixture of tunnel and layered crystal structures. NaAl(0.1) Mn(0.9) O2 shows a much higher initial discharge capacity and superior cycling performance compared to pristine Na(0.65) MnO2 . We ascribe this enhancement in performance to the formation of a new orthorhombic layered NaMnO2 phase merged with a small amount of tunnel Na(0.44) MnO2 phase in NaAl(0.1) Mn(0.9) O2 , and to improvements in the surface stability of the NaAl(0.1) Mn(0.9) O2 particles caused by the formation of Al-O bonds on their surfaces. Our findings regarding the phase transformation and structure stabilization induced by incorporation of aluminum, closely related to the structural analogy between orthorhombic Na(0.44) MnO2 and NaAl(0.1) Mn(0.9) O2 , suggest a strategy for achieving sodium rechargeable batteries with high energy density and stability. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Influence of monitor luminance and room illumination on soft-copy reading evaluation with electronically generated contrast-detail phantom: comparison of cathode-ray tube monitor with liquid crystal display.

PubMed

Muramoto, Hideyuki; Shimamoto, Kazuhiro; Ikeda, Mitsuru; Koyama, Kazuyuki; Fukushima, Hiromichi; Ishigaki, Takeo

2006-06-01

The influence of monitor brightness and room illumination on soft-copy diagnosis by both cathode-ray tube (CRT) monitor and liquid crystal display (LCD) was evaluated and compared using a contrast-detail phantom. Nine observers (7 radiologists and 2 radiological technicians) interpreted six types of electronically generated contrast-detail phantom images using a 21-inch CRT (2,048x2,560) and a 21-inch LCD (2,048x2,560) under 6 kinds of viewing conditions, i.e. monitor brightness of 330 cd/m2 or 450 cd/m2, and room illumination of 20, 100 or 420 lux at the center of the display. Observers were requested to determine the visible borderline of the objects. Between 330 cd/m2 and 450 cd/m2, no significant difference in the visible area was found under any of the three lighting conditions. However, in two low-contrast phantom images, the visible area on the LCD was significantly larger than that on the CRT, independent of both monitor brightness and room illumination. (p<0.05). The effect of room illumination was not significant, suggesting that the use of LCD at high room illumination is acceptable.

Immobilization of uranium into magnetite from aqueous solution by electrodepositing approach.

PubMed

Lu, Bing-Qing; Li, Mi; Zhang, Xiao-Wen; Huang, Chun-Mei; Wu, Xiao-Yan; Fang, Qi

2018-02-05

Immobilization of uranium into magnetite (Fe 3 O 4 ), which was generated from metallic iron by electrochemical method, was proposed to rapidly remove uranium from aqueous solution. The effects of electrochemical parameters such as electrode materials, voltage, electrode gap, reaction time and pH value on the crystallization of Fe 3 O 4 and uranium removal efficiencies were investigated. More than 90% uranium in the solution was precipitated with Fe 3 O 4 under laboratory conditions when uranium concentration range from 0.5mg/L to 10mg/L. The Fe 3 O 4 crystallization mechanism and immobilization of uranium was proved by XPS, XRD, TEM, FTIR and VSM methods. The results indicated that the cationic (including Fe 2+ , Fe 3+ and U(VI)) migrate to cathode side under the electric field and the uranium was incorporated or adsorbed by Fe 3 O 4 which was generated at cathode while the pH ranges between 2-7. The uranium-containing precipitate of Fe 3 O 4 can exist stably at the acid concentration below 60g/L. Furthermore, the precipitate may be used as valuable resources for uranium or iron recycling, which resulted in no secondary pollution in the removal of uranium from aqueous solution. Copyright © 2017. Published by Elsevier B.V.

Reduction-melting combined with a Na₂CO₃ flux recycling process for lead recovery from cathode ray tube funnel glass.

PubMed

Okada, Takashi; Yonezawa, Susumu

2014-08-01

With large quantity of flux (Na2CO3), lead can be recovered from the funnel glass of waste cathode-ray tubes via reduction-melting at 1000°C. To reduce flux cost, a technique to recover added flux from the generated oxide phase is also important in order to recycle the flux recovered from the reduction-melting process. In this study, the phase separation of sodium and the crystallization of water-soluble sodium silicates were induced after the reduction-melting process to enhance the leachability of sodium in the oxide phase and to extract the sodium from the phase for the recovery of Na2CO3 as flux. A reductive atmosphere promoted the phase separation and crystallization, and the leachability of sodium from the oxide phase was enhanced. The optimum temperature and treatment time for increasing the leachability were 700°C and 2h, respectively. After treatment, more than 90% of the sodium in the oxide phase was extracted in water. NaHCO3 can be recovered by carbonization of the solution containing sodium ions using carbon dioxide gas, decomposed to Na2CO3 at 50°C and recycled for use in the reduction-melting process. Copyright © 2014 Elsevier Ltd. All rights reserved.

Development of a trickle bed reactor of electro-Fenton process for wastewater treatment.

PubMed

Lei, Yangming; Liu, Hong; Shen, Zhemin; Wang, Wenhua

2013-10-15

To avoid electrolyte leakage and gas bubbles in the electro-Fenton (E-Fenton) reactors using a gas diffusion cathode, we developed a trickle bed cathode by coating a layer composed of carbon black and polytetrafluoroethylene (C-PTFE) onto graphite chips instead of carbon cloth. The trickle bed cathode was optimized by single-factor and orthogonal experiments, in which carbon black, PTFE, and a surfactant were considered as the determinant of the performance of graphite chips. In the reactor assembled by the trickle bed cathode, H2O2 was generated with a current of 0.3A and a current efficiency of 60%. This performance was attributed to the fine distribution of electrolyte and air, as well as the effective oxygen transfer from the gas phase to the electrolyte-cathode interface. In terms of H2O2 generation and current efficiency, the developed trickle bed reactor had a performance comparable to that of the conventional E-Fenton reactor using a gas diffusion cathode. Further, 123 mg L(-1) of reactive brilliant red X-3B in aqueous solution was decomposed in the optimized trickle bed reactor as E-Fenton reactor. The decolorization ratio reached 97% within 20 min, and the mineralization reached 87% within 3h. Copyright © 2013 Elsevier B.V. All rights reserved.

Characteristics of a velvet cathode under high repetition rate pulse operation

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

Xun Tao; Zhang Jiande; Yang Hanwu

2009-10-15

As commonly used material for cold cathodes, velvet works well in single shot and low repetition rate (rep-rate) high-power microwave (HPM) sources. In order to determine the feasibility of velvet cathodes under high rep-rate operation, a series of experiments are carried out on a high-power diode, driven by a {approx}300 kV, {approx}6 ns, {approx}100 {omega}, and 1-300 Hz rep-rate pulser, Torch 02. Characteristics of vacuum compatibility and cathode lifetime under different pulse rep-rate are focused on in this paper. Results of time-resolved pressure history, diode performance, shot-to-shot reproducibility, and velvet microstructure changes are presented. As the rep-rate increases, the equilibriummore » pressure grows hyperlinearly and the velvet lifetime decreases sharply. At 300 Hz, the pressure in the given diode exceeded 1 Pa, and the utility shots decreased to 2000 pulses for nonstop mode. While, until the velvet begins to degrade, the pulse-to-pulse instability of diode voltage and current is quite small, even under high rep-rate conditions. Possible reasons for the operation limits are discussed, and methods to improve the performance of a rep-rate velvet cathode are also suggested. These results may be of interest to the repetitive HPM systems with cold cathodes.« less

Electrochemical characterization of B-site cation-excess Pr 2Ni 0.75Cu 0.25Ga 0.05O 4+δ cathode for IT-SOFCs

DOE PAGES

Meng, Xiangwei; Lü, Shiquan; Liu, Shouxiu; ...

2015-06-15

In this paper, the B-site cation-excess K 2NiF 4-type structure oxide, Pr 2Ni 0.75Cu 0.25Ga 0.05O 4+δ (PNCG) is investigated as a cathode for intermediate-temperature solid oxide fuel cells (IT-SOFCs). XRD result shows that PNCG cathode is chemically compatible with the electrolyte Gd 0.1Ce 0.9O 2-δ (GDC) at 900 °C for 5 h. The PNCG material exhibits a semiconductor to metal transition around 425 °C. The thermal expansion coefficient (TEC) of the PNCG sample is 12.72×10 -6 K -1 between 30 and 850 °C in air. The polarization resistance (R p) of PNCG cathode on GDC electrolyte is 0.105, 0.197more » and 0.300 Ω cm 2 at 800, 750, 700 °C, respectively. A maximum power density of 371 mW cm -2 is obtained at 800 °C for single-cell with 300 μm thick GDC electrolyte and PNCG cathode. Finally, the results of this study demonstrate that PNCG can be a promising cathode material for IT-SOFCs.« less

Robust diamond-like Fe-Si network in the zero-strain Na xFeSiO 4 cathode

DOE PAGES

Ye, Zhuo; Zhao, Xin; Li, Shouding; ...

2016-07-14

Sodium orthosilicates Na 2 MSiO 4 ( M denotes transition metals) have attracted much attention due to the possibility of exchanging two electrons per formula unit. In this work, we report a group of sodium iron orthosilicates Na 2FeSiO 4. Their crystal structures are characterized by a diamond-like Fe-Si network. The Fe-Si network is quite robust against the charge/discharge process, which explains the high structural stability observed in experiment. Furthermore, using the density functional theory within the GGA + U framework and X-ray diffraction studies, the crystal structures and structural stabilities during the sodium extraction/re-insertion process are systematically investigated.

Microstructure and pinning properties of hexagonal-disc shaped single crystalline MgB2

NASA Astrophysics Data System (ADS)

Jung, C. U.; Kim, J. Y.; Chowdhury, P.; Kim, Kijoon H.; Lee, Sung-Ik; Koh, D. S.; Tamura, N.; Caldwell, W. A.; Patel, J. R.

2002-11-01

We synthesized hexagonal-disc-shaped MgB2 single crystals under high-pressure conditions and analyzed the microstructure and pinning properties. The lattice constants and the Laue pattern of the crystals from x-ray micro-diffraction showed the crystal symmetry of MgB2. A thorough crystallographic mapping within a single crystal showed that the edge and c axis of hexagonal-disc shape exactly matched the [101¯0] and the [0001] directions of the MgB2 phase. Thus, these well-shaped single crystals may be the best candidates for studying the direction dependences of the physical properties. The magnetization curve and the magnetic hysteresis curve for these single crystals showed the existence of a wide reversible region and weak pinning properties, which supported our single crystals being very clean.

Growth and microtopographic study of CuInSe{sub 2} single crystals

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

Chauhan, Sanjaysinh M.; Chaki, Sunil, E-mail: sunilchaki@yahoo.co.in; Deshpande, M. P.

2016-05-23

The CuInSe{sub 2} single crystals were grown by chemical vapour transport (CVT) technique using iodine as transporting agent. The elemental composition of the as-grown CuInSe{sub 2} single crystals was determined by energy dispersive analysis of X-ray (EDAX). The unit cell crystal structure and lattice parameters were determined by X-ray diffraction (XRD) technique. The surface microtopographic study of the as-grown CuInSe{sub 2} single crystals surfaces were done to study the defects, growth mechanism, etc. of the CVT grown crystals.

Method for the preparation of inorganic single crystal and polycrystalline electronic materials

NASA Technical Reports Server (NTRS)

Groves, W. O. (Inventor)

1969-01-01

Large area, semiconductor crystals selected from group 3-5 compounds and alloys are provided for semiconductor device fabrication by the use of a selective etching operation which completely removes the substrate on which the desired crystal was deposited. The substrate, selected from the same group as the single crystal, has a higher solution rate than the epitaxial single crystal which is essentially unaffected by the etching solution. The preparation of gallium phosphide single crystals using a gallium arsenide substrate and a concentrated nitric acid etching solution is described.

Porosity Evolution in a Creeping Single Crystal (Preprint)

DTIC Science & Technology

2012-08-01

1] indicated that the growth of initially present processing induced voids in a nickel based single crystal superalloy played a significant role in...processing induced voids in a nickel based single crystal superalloy played a significant role in limiting creep life. Also, creep tests on single...experimental observations of creep deformation and failure of a nickel based single crystal superalloy, [1, 2]. Metallographic observations have shown that Ni

Co-intercalation of Mg(2+) and Na(+) in Na(0.69)Fe2(CN)6 as a High-Voltage Cathode for Magnesium Batteries.

PubMed

Kim, Dong-Min; Kim, Youngjin; Arumugam, Durairaj; Woo, Sang Won; Jo, Yong Nam; Park, Min-Sik; Kim, Young-Jun; Choi, Nam-Soon; Lee, Kyu Tae

2016-04-06

Thanks to the advantages of low cost and good safety, magnesium metal batteries get the limelight as substituent for lithium ion batteries. However, the energy density of state-of-the-art magnesium batteries is not high enough because of their low operating potential; thus, it is necessary to improve the energy density by developing new high-voltage cathode materials. In this study, nanosized Berlin green Fe2(CN)6 and Prussian blue Na(0.69)Fe2(CN)6 are compared as high-voltage cathode materials for magnesium batteries. Interestingly, while Mg(2+) ions cannot be intercalated in Fe2(CN)6, Na(0.69)Fe2(CN)6 shows reversible intercalation and deintercalation of Mg(2+) ions, although they have the same crystal structure except for the presence of Na(+) ions. This phenomenon is attributed to the fact that Mg(2+) ions are more stable in Na(+)-containing Na(0.69)Fe2(CN)6 than in Na(+)-free Fe2(CN)6, indicating Na(+) ions in Na(0.69)Fe2(CN)6 plays a crucial role in stabilizing Mg(2+) ions. Na(0.69)Fe2(CN)6 delivers reversible capacity of approximately 70 mA h g(-1) at 3.0 V vs Mg/Mg(2+) and shows stable cycle performance over 35 cycles. Therefore, Prussian blue analogues are promising structures for high-voltage cathode materials in Mg batteries. Furthermore, this co-intercalation effect suggests new avenues for the development of cathode materials in hybrid magnesium batteries that use both Mg(2+) and Na(+) ions as charge carriers.

The 15 cm mercury ion thruster research 1975

NASA Technical Reports Server (NTRS)

Wilbur, P. J.

1975-01-01

Doubly charged ion current measurements in the beam of a SERT II thruster are shown to introduce corrections which bring its calculated thrust into close agreement with that measured during flight testing. A theoretical model of doubly charged ion production and loss in mercury electron bombardment thrusters is discussed and is shown to yield doubly-to-singly charged ion density ratios that agree with experimental measurements obtained on a 15 cm diameter thruster over a range of operating conditions. Single cusp magnetic field thruster operation is discussed and measured ion beam profiles, performance data, doubly charged ion densities, and discharge plasma characteristics are presented for a range of operating conditions and thruster geometries. Variations in the characteristics of this thruster are compared to those observed in the divergent field thruster and the cusped field thruster is shown to yield flatter ion beam profiles at about the same discharge power and propellant utilization operating point. An ion optics test program is described and the measured effects of grid system dimensions on ion beamlet half angle and diameter are examined. The effectiveness of hollow cathode startup using a thermionically emitting filament within the cathode is examined over a range of mercury flow rates and compared to results obtained with a high voltage tickler startup technique. Results of cathode plasma property measurement tests conducted within the cathode are presented.

Growth and surface topography of WSe{sub 2} single crystal

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

Dixit, Vijay, E-mail: vijdix1@gmail.com; Vyas, Chirag; Pataniya, Pratik

2016-05-06

Tungsten Di-Selenide belongs to the family of TMDCs showing their potential applications in the fields of Optoelectronics and PEC solar cells. Here in the present investigation single crystals of WSe{sub 2} were grown by Direct Vapour Transport Technique in a dual zone furnace having temperature difference of 50 K between the two zones. These single crystals were characterized by EDAX which confirms the stiochiometry of the grown crystals. Surface topography of the crystal was studied by optical micrograph showing the left handed spirals on the surface of WSe{sub 2} crystals. Single crystalline nature of the crystals was confirmed by SAED.

Minimal RED cell pairs markedly improve electrode kinetics and power production in microbial reverse electrodialysis cells.

PubMed

Cusick, Roland D; Hatzell, Marta; Zhang, Fang; Logan, Bruce E

2013-12-17

Power production from microbial reverse electrodialysis cell (MRC) electrodes is substantially improved compared to microbial fuel cells (MFCs) by using ammonium bicarbonate (AmB) solutions in multiple RED cell pair stacks and the cathode chamber. Reducing the number of RED membranes pairs while maintaining enhanced electrode performance could help to reduce capital costs. We show here that using only a single RED cell pair (CP), created by operating the cathode in concentrated AmB, dramatically increased power production normalized to cathode area from both acetate (Acetate: from 0.9 to 3.1 W/m(2)-cat) and wastewater (WW: 0.3 to 1.7 W/m(2)), by reducing solution and charge transfer resistances at the cathode. A second RED cell pair increased RED stack potential and reduced anode charge transfer resistance, further increasing power production (Acetate: 4.2 W/m(2); WW: 1.9 W/m(2)). By maintaining near optimal electrode power production with fewer membranes, power densities normalized to total membrane area for the 1-CP (Acetate: 3.1 W/m(2)-mem; WW: 1.7 W/m(2)) and 2-CP (Acetate: 1.3 W/m(2)-mem; WW: 0.6 W/m(2)) reactors were much higher than previous MRCs (0.3-0.5 W/m(2)-mem with acetate). While operating at peak power, the rate of wastewater COD removal, normalized to reactor volume, was 30-50 times higher in 1-CP and 2-CP MRCs than that in a single chamber MFC. These findings show that even a single cell pair AmB RED stack can significantly enhance electrical power production and wastewater treatment.

Ultrathin solution-processed single crystals of thiophene-phenylene co-oligomers for organic field-effect devices

NASA Astrophysics Data System (ADS)

Glushkova, Anastasia V.; Poimanova, Elena Yu.; Bruevich, Vladimir V.; Luponosov, Yuriy N.; Ponomarenko, Sergei A.; Paraschuk, Dmitry Yu.

2017-08-01

Thiophene-phenylene co-oligomers (TPCO) single crystals are promising materials for organic light-emitting devices, e.g., light-emitting transistors (OLETs), due to their ability to combine high luminescence and efficient charge transport. However, optical confinement in platy single crystals strongly decreases light emission from their top surface degrading the device performance. To avoid optical waveguiding, single crystals thinner than 100 nm would be beneficial. Herein, we report on solution-processed ultrathin single crystals of TPCO and study their charge transport properties. As materials we used 1,4-bis(5'-hexyl-2,2'-bithiophene-5-yl)benzene (DH-TTPTT) and 1,4-bis(5'-decyl-2,2'-bithiophene-5-yl)benzene (DD-TTPTT). The ultrathin single crystals were studied by optical polarization, atomic-force, and transmission electron microscopies, and as active layers in organic field effect transistors (OFET). The OFET hole mobility was increased tenfold for the oligomer with longer alkyl substituents (DD-TTPTT) reaching 0.2 cm2/Vs. Our studies of crystal growth indicate that if the substrate is wetted, it has no significant effect on the crystal growth. We conclude that solution-processed ultrathin TPCO single crystals are a promising platform for organic optoelectronic field-effect devices.

Nanoparticles Incorporated inside Single-Crystals: Enhanced Fluorescent Properties

DOE PAGES

Liu, Yujing; Zang, Huidong; Wang, Ling; ...

2016-09-25

Incorporation of guest materials inside single-crystalline hosts leads to single-crystal composites that have become more and more frequently seen in both biogenic and synthetic crystals. The unique composite structure together with long-range ordering promises special properties that are, however, less often demonstrated. In this study, we examine the fluorescent properties of quantum dots (QDs) and polymer dots (Pdots) encapsulated inside the hosts of calcite single-crystals. Two CdTe QDs and two Pdots are incorporated into growing calcite crystals, as the QDs and Pdots are dispersed in the crystallization media of agarose gels. As a result, enhanced fluorescent properties are obtained frommore » the QDs and Pdots inside calcite single-crystals with greatly improved photostability and significantly prolonged fluorescence lifetime, compared to those in solutions and gels. Particularly, the fluorescence lifetime increases by 0.5-1.6 times after the QDs or Pdots are incorporated. The enhanced fluorescent properties indicate the advantages of encapsulation by single-crystal hosts that provide dense shells to isolate the fluorescent nanoparticles from atmosphere. As such, this work has implications for advancing the research of single-crystal composites toward their functional design.« less

Solar cell structure incorporating a novel single crystal silicon material

DOEpatents

Pankove, Jacques I.; Wu, Chung P.

1983-01-01

A novel hydrogen rich single crystal silicon material having a band gap energy greater than 1.1 eV can be fabricated by forming an amorphous region of graded crystallinity in a body of single crystalline silicon and thereafter contacting the region with atomic hydrogen followed by pulsed laser annealing at a sufficient power and for a sufficient duration to recrystallize the region into single crystal silicon without out-gassing the hydrogen. The new material can be used to fabricate semiconductor devices such as single crystal silicon solar cells with surface window regions having a greater band gap energy than that of single crystal silicon without hydrogen.

Crystal growth, structural, thermal and mechanical behavior of l-arginine 4-nitrophenolate 4-nitrophenol dihydrate (LAPP) single crystals.

PubMed

Mahadevan, M; Ramachandran, K; Anandan, P; Arivanandhan, M; Bhagavannarayana, G; Hayakawa, Y

2014-12-10

Single crystals of l-arginine 4-nitrophenolate 4-nitrophenol dihydrate (LAPP) have been grown successfully from the solution of l-arginine and 4-nitrophenol. Slow evaporation of solvent technique was adopted to grow the bulk single crystals. Single crystal X-ray diffraction analysis confirms the grown crystal has monoclinic crystal system with space group of P21. Powder X-ray diffraction analysis shows the good crystalline nature. The crystalline perfection of the grown single crystals was analyzed by HRXRD by employing a multicrystal X-ray diffractometer. The functional groups were identified from proton NMR spectroscopic analysis. Linear and nonlinear optical properties were determined by UV-Vis spectrophotometer and Kurtz powder technique respectively. It is found that the grown crystal has no absorption in the green wavelength region and the SHG efficiency was found to be 2.66 times that of the standard KDP. The Thermal stability of the crystal was found by obtaining TG/DTA curve. The mechanical behavior of the grown crystal has been studied by Vicker's microhardness method. Copyright © 2014 Elsevier B.V. All rights reserved.

Microtube-Czochralski technique (μT-CZ):. a novel way of seeding the melt to grow bulk single crystal

NASA Astrophysics Data System (ADS)

Sankaranarayanan, K.; Ramasamy, P.

1998-09-01

A novel microtube seeding has been proposed in the conventional Czochralski pulling technique to grow a bulk single crystal. The versatility of the technique has been shown by adopting this method for the growth of benzil. Benzil single crystals having hexagonal facets are grown by this technique called the microtube-Czochralski technique (μT-CZ). Due to capillary rise, a fine column of melt was crystallized inside the microtube, which leads to the formation of the single crystal nucleation and ends up with hexagonal morphology. The reproducibility for getting single crystal is about 80%. It is evident that this technique is more viable to grow a bulk single crystal from the melt without a pregrown-seed. Further, the proposed μT-CZ technique can also be extended to other newer materials with the proper choice of the microtube.

Small polaron hopping conduction mechanism in LiFePO4 glass and crystal

NASA Astrophysics Data System (ADS)

Banday, Azeem; Murugavel, Sevi

2017-01-01

The optimization of a cathode material is the most important criterion of lithium ion battery technology, which decides the power density. In order to improve the rate capability, a cathode material must possess high electronic and ionic conductivities. Therefore, it is important to understand the charge transport mechanism in such an advanced cathode material in its intrinsic state before modifying it by various means. In this work, we report the thermal, structural, and electrical conductivity studies on lithium iron phosphate, LiFePO4, both in its polycrystalline (LFPC) and glassy (LFPG) counterpart states. The vibrational spectroscopic measurements reveal the characteristic vibrational modes, which are the intrinsic part of LFPC, whereas in LFPG, the phonon modes become broader and overlap with each other due to the lattice disorder. The electrical conductivity measurements reveal that LFPG exhibits a higher polaronic conductivity of 1.6 orders than the LFPC sample. The temperature dependent dc conductivity has been analyzed with the Mott model of polarons and reveals the origin of enhanced polaronic conductivity in LFPG. Based on the analysis, the enhanced polaronic conductivity in LFPG has been attributed to the combined effect of reduced hopping length, decreased activation energy, and enhanced polaron concentration.

3-D dumbbell-like LiNi1/3Mn1/3Co1/3O2 cathode materials assembled with nano-building blocks for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Ryu, Won-Hee; Lim, Sung-Jin; Kim, Won-Keun; Kwon, HyukSang

2014-07-01

Dumbbell-like microsphere carbonate precursors including multi-transition metal components (Ni1/3Mn1/3Co1/3CO3) assembled with nano-building blocks were synthesized by urea-assisted solvo/hydrothermal method, and layered cathode materials (LiNi1/3Mn1/3Co1/3O2) were subsequently prepared using the similarly shaped carbonate precursors for Li-ion batteries. For the synthesis of hierarchical microsphere structures, the partial addition of viscous organic solvent (e.g. ethylene glycol) in aqueous solution played a crucial role, not only in suppressing the sudden particle growth but also in regulating the directional crystallization of carbonate particles on the surface. The dumbbell-like LiNi1/3Mn1/3Co1/3O2 assembled with nanocubes prepared via the urea-assisted solvo/hydrothermal method exhibited better electrochemical characteristics, such as initial discharge capacity, cyclic performance, and rate-capability as a cathode material of Li-ion batteries, compared with the LiNi1/3Mn1/3Co1/3O2 materials prepared via the conventional co-precipitation method.

In-situ Crystallization of Highly Volatile Commercial Mold Flux Using an Isolated Observation System in the Confocal Laser Scanning Microscope

NASA Astrophysics Data System (ADS)

Park, Jun-Yong; Ryu, Jae Wook; Sohn, Il

2014-08-01

The in situ crystallization behavior of highly volatile commercial mold fluxes for medium carbon steels was investigated using the confocal laser scanning microscope (CLSM) equipped with an optimized isolated observation system. The highly volatile compounds of the mold flux were suppressed during heating allowing direct observation in the CLSM. Cooling rates of 25, 50, 100, 400, and 800 K/min were incorporated and continuous cooling transformation (CCT) diagrams of 4 different commercial mold fluxes for medium carbon steels were developed. Identification of the crystalline phase was conducted with XRD and SEM-EDS analysis. A cuspidine crystalline was observed in all samples at various cooling rates. With higher basicity, CaF2, and NaF, the crystallization of the fluxes was enhanced according to the CCT diagram. As the slag structure becomes depolymerized, the diffusion rate of the cathodic ions seems to increase.

Preliminary investigation of single chamber single electrode microbial fuel cell using sewage sludge as a substrate

NASA Astrophysics Data System (ADS)

Sai Chaithanya, M.; Thakur, Somil; Sonu, Kumar; Das, Bhaskar

2017-11-01

A microbial fuel cell (MFC) consists of a cathode and anode; micro-organisms transfer electrons acquired from the degradation of organic matter in the substrate to anode; and thereby to cathode; by using an external circuit to generate electricity. In the present study, a single chamber single electrode microbial fuel cell has been fabricated to generate electricity from the sludge of the sewage treatment plant at two different ambient temperature range of 25 ± 4°C and 32 ± 4°C under aerobic condition. No work has been done yet by using the single electrode in any MFC system; it is hypothesized that single electrode submerged partially in substrate and rest to atmosphere can function as both cathode and anode. The maximum voltage obtained was about 2890 mV after 80 (hrs) at temperature range of 25 ± 4°C, with surface power density of 1108.29 mW/m2. When the ambient temperature was 32 ± 4°C, maximum voltage obtained was 1652 mV after 40 (hrs.) surface power density reduced to 865.57 mW/m2. When amount of substrate was decreased for certain area of electrode at 25 ± 4°C range, electricity generation decreased and it also shortened the time to reach peak voltage. On the other hand, when the ambient temperature was increased to 32 ± 4°C, the maximum potential energy generated was less than that of previous experiment at 25 ± 4°C for the same substrate Also the time to reach peak voltage decreased to 40 hrs. When comparing with other single chamber single electrode MFC, the present model is generating more electricity that any MFC using sewage sludge as substrate except platinum electrode, which is much costlier that electrode used in the present study.

Effect of Chain Conformation on the Single-Molecule Melting Force in Polymer Single Crystals: Steered Molecular Dynamics Simulations Study.

PubMed

Feng, Wei; Wang, Zhigang; Zhang, Wenke

2017-02-28

Understanding the relationship between polymer chain conformation as well as the chain composition within the single crystal and the mechanical properties of the corresponding single polymer chain will facilitate the rational design of high performance polymer materials. Here three model systems of polymer single crystals, namely poly(ethylene oxide) (PEO), polyethylene (PE), and nylon-66 (PA66) have been chosen to study the effects of chain conformation, helical (PEO) versus planar zigzag conformation (PE, PA66), and chain composition (PE versus PA66) on the mechanical properties of a single polymer chain. To do that, steered molecular dynamics simulations were performed on those polymer single crystals by pulling individual polymer chains out of the crystals. Our results show that the patterns of force-extension curve as well as the chain moving mode are closely related to the conformation of the polymer chain in the single crystal. In addition, hydrogen bonds can enhance greatly the force required to stretch the polymer chain out of the single crystal. The dynamic breaking and reformation of multivalent hydrogen bonds have been observed for the first time in PA66 at the single molecule level.

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

Patel, J. R.

We synthesized hexagonal-disc-shaped MgB{sub 2} single crystals under high-pressure conditions and analyzed the microstructure and pinning properties. The lattice constants and the Laue pattern of the crystals from X-ray micro-diffraction showed the crystal symmetry of MgB{sub 2}. A thorough crystallographic mapping within a single crystal showed that the edge and c-axis of hexagonal-disc shape exactly matched the (10-10) and the (0001) directions of the MgB{sub 2} phase. Thus, these well-shaped single crystals may be the best candidates for studying the direction dependences of the physical properties. The magnetization curve and the magnetic hysteresis for these single crystals showed the existencemore » of a wide reversible region and weak pinning properties, which supported our single crystals being very clean.« less

Uranium dioxide electrolysis

DOEpatents

Willit, James L [Batavia, IL; Ackerman, John P [Prescott, AZ; Williamson, Mark A [Naperville, IL

2009-12-29

This is a single stage process for treating spent nuclear fuel from light water reactors. The spent nuclear fuel, uranium oxide, UO.sub.2, is added to a solution of UCl.sub.4 dissolved in molten LiCl. A carbon anode and a metallic cathode is positioned in the molten salt bath. A power source is connected to the electrodes and a voltage greater than or equal to 1.3 volts is applied to the bath. At the anode, the carbon is oxidized to form carbon dioxide and uranium chloride. At the cathode, uranium is electroplated. The uranium chloride at the cathode reacts with more uranium oxide to continue the reaction. The process may also be used with other transuranic oxides and rare earth metal oxides.

Single-crystal silicon optical fiber by direct laser crystallization

DOE PAGES

Ji, Xiaoyu; Lei, Shiming; Yu, Shih -Ying; ...

2016-12-05

Semiconductor core optical fibers with a silica cladding are of great interest in nonlinear photonics and optoelectronics applications. Laser crystallization has been recently demonstrated for crystallizing amorphous silicon fibers into crystalline form. Here we explore the underlying mechanism by which long single-crystal silicon fibers, which are novel platforms for silicon photonics, can be achieved by this process. Using finite element modeling, we construct a laser processing diagram that reveals a parameter space within which single crystals can be grown. Utilizing this diagram, we illustrate the creation of single-crystal silicon core fibers by laser crystallizing amorphous silicon deposited inside silica capillarymore » fibers by high-pressure chemical vapor deposition. The single-crystal fibers, up to 5.1 mm long, have a very welldefined core/cladding interface and a chemically pure silicon core that leads to very low optical losses down to ~0.47-1dB/cm at the standard telecommunication wavelength (1550 nm). Furthermore, tt also exhibits a photosensitivity that is comparable to bulk silicon. Creating such laser processing diagrams can provide a general framework for developing single-crystal fibers in other materials of technological importance.« less

Fundamental Investigations and Rational Design of Durable High-Performance SOFC Cathodes

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

Chen, Yu; Ding, Dong; Wei, Tao

The main objective of this project is to unravel the degradation mechanism of LSCF cathodes under realistic operating conditions with different types of contaminants, aiming towards the rational design of cathodes with high-performance and enhanced durability by combining a porous backbone (such as LSCF) with a thin catalyst coating. The mechanistic understanding will help us to optimize the composition and morphology of the catalyst layer and microstructure of the LSCF backbone for better performance and durability. More specifically, the technical objectives include: (1) to unravel the degradation mechanism of LSCF cathodes under realistic operating conditions with different types of contaminantsmore » using in situ and ex situ measurements performed on specially-designed cathodes; (2) to examine the microstructural and compositional evolution of LSCF cathodes as well as the cathode/electrolyte interfaces under realistic operating conditions; (3) to correlate the fuel cell performance instability and degradation with the microstructural and morphological evolution and surface chemistry change of the cathode under realistic operating conditions; (4) to explore new catalyst materials and electrode structures to enhance the stability of the LSCF cathode under realistic operating conditions; and (5) to validate the long term stability of the modified LSCF cathode in commercially available cells under realistic operating conditions. We have systematically evaluated LSCF cathodes in symmetrical cells and anode supported cells under realistic conditions with different types of contaminants such as humidity, CO 2, and Cr. Electrochemical models for the design of test cells and understanding of mechanisms have been developed for the exploration of fundamental properties of electrode materials. It is demonstrated that the activity and stability of LSCF cathodes can be degraded by the introduction of contaminants. The microstructural and compositional evolution of LSCF cathodes as well as the cathode/electrolyte interfaces under realistic operating conditions has been studied. It is found that SrO readily segregated/enriched on the LSCF surface. More severe contamination conditions cause more SrO on surface. Novel catalyst coatings through particle depositions (PrOx) or continuous thin films (PNM) were successfully developed to improve the activity and stability of LSCF cathodes. Finally, we have demonstrated enhanced activity and stability of LSCF cathodes over longer periods of time in homemade and commercially available cells by an optimized PNM (dense film and particles) infiltration process, under clean air and realistic operating conditions (3% H 2O, 5% CO 2 and direct Crofer contact). Both performance and durability of single cells with PNM coating has been enhanced compared with those without coating. Raman analysis of cathodes surface indicated that the intensity of SrCrO 4 was significantly decreased.« less

Formation of curved micrometer-sized single crystals.

PubMed

Koifman Khristosov, Maria; Kabalah-Amitai, Lee; Burghammer, Manfred; Katsman, Alex; Pokroy, Boaz

2014-05-27

Crystals in nature often demonstrate curved morphologies rather than classical faceted surfaces. Inspired by biogenic curved single crystals, we demonstrate that gold single crystals exhibiting curved surfaces can be grown with no need of any fabrication steps. These single crystals grow from the confined volume of a droplet of a eutectic composition melt that forms via the dewetting of nanometric thin films. We can control their curvature by controlling the environment in which the process is carried out, including several parameters, such as the contact angle and the curvature of the drops, by changing the surface tension of the liquid drop during crystal growth. Here we present an energetic model that explains this phenomenon and predicts why and under what conditions crystals will be forced to grow with the curvature of the microdroplet even though the energetic state of a curved single crystal is very high.

Capillarity creates single-crystal calcite nanowires from amorphous calcium carbonate.

PubMed

Kim, Yi-Yeoun; Hetherington, Nicola B J; Noel, Elizabeth H; Kröger, Roland; Charnock, John M; Christenson, Hugo K; Meldrum, Fiona C

2011-12-23

Single-crystal calcite nanowires are formed by crystallization of morphologically equivalent amorphous calcium carbonate (ACC) particles within the pores of track etch membranes. The polyaspartic acid stabilized ACC is drawn into the membrane pores by capillary action, and the single-crystal nature of the nanowires is attributed to the limited contact of the intramembrane ACC particle with the bulk solution. The reaction environment then supports transformation to a single-crystal product. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Laser radiation frequency doubling in a single-crystal fibre based on a stoichiometric LiNbO3 crystal

NASA Astrophysics Data System (ADS)

Kashin, V. V.; Nikolaev, D. A.; Rusanov, S. Ya; Tsvetkov, V. B.

2015-01-01

We demonstrate the employment of single-crystal optical fibres based on lithium niobate for doubling the laser radiation frequency. The measured characteristics of the fibre confirm its high quality and spatial homogeneity. Parameters of the frequency doublers for neodymium laser radiation (λ = 1 mm) based on fibre and bulk single crystals are compared. Single crystals are grown by the method of laser-heated pedestal growing with heating by radiation of a CO2 laser (LHPG-method).

Effect of L-Valine on the growth and characterization of Sodium Acid Phthalate (SAP) single crystals.

PubMed

Nirmala, L Ruby; Thomas Joseph Prakash, J

2013-06-01

Undoped and amino acid doped good quality single crystals of Sodium Acid Phthalate crystals (SAP) were grown by slow evaporation solution growth technique which are semiorganic in nature. The effect of amino acid (L-Valine) dopant on the growth and the properties of SAP single crystal was investigated. The single crystal X-ray diffraction studies and FT-IR studies were carried out to identify the crystal structure and the presence of functional groups in undoped and L-Valine doped SAP crystals. The transparent nature of the grown crystal was observed using UV-Visible spectrum. The thermal decomposition of the doped SAP crystals was investigated by thermo gravimetric analysis (TGA) and differential thermal analysis (DTA). The enhancement in the NLO property of the undoped and L-Valine doped SAP crystals using KDP crystal as a reference was studied using SHG measurements. Vickers micro hardness measurements are used for the study of mechanical strength of the grown crystals. Copyright © 2013 Elsevier B.V. All rights reserved.

Positioning and joining of organic single-crystalline wires

PubMed Central

Wu, Yuchen; Feng, Jiangang; Jiang, Xiangyu; Zhang, Zhen; Wang, Xuedong; Su, Bin; Jiang, Lei

2015-01-01

Organic single-crystal, one-dimensional materials can effectively carry charges and/or excitons due to their highly ordered molecule packing, minimized defects and eliminated grain boundaries. Controlling the alignment/position of organic single-crystal one-dimensional architectures would allow on-demand photon/electron transport, which is a prerequisite in waveguides and other optoelectronic applications. Here we report a guided physical vapour transport technique to control the growth, alignment and positioning of organic single-crystal wires with the guidance of pillar-structured substrates. Submicrometre-wide, hundreds of micrometres long, highly aligned, organic single-crystal wire arrays are generated. Furthermore, these organic single-crystal wires can be joined within controlled angles by varying the pillar geometries. Owing to the controllable growth of organic single-crystal one-dimensional architectures, we can present proof-of-principle demonstrations utilizing joined wires to allow optical waveguide through small radii of curvature (internal angles of ~90–120°). Our methodology may open a route to control the growth of organic single-crystal one-dimensional materials with potential applications in optoelectronics. PMID:25814032

Surfing Silicon Nanofacets for Cold Cathode Electron Emission Sites.

PubMed

Basu, Tanmoy; Kumar, Mohit; Saini, Mahesh; Ghatak, Jay; Satpati, Biswarup; Som, Tapobrata

2017-11-08

Point sources exhibit low threshold electron emission due to local field enhancement at the tip. In the case of silicon, however, the realization of tip emitters has been hampered by unwanted oxidation, limiting the number of emission sites and the overall current. In contrast to this, here, we report the fascinating low threshold (∼0.67 V μm -1 ) cold cathode electron emission from silicon nanofacets (Si-NFs). The ensembles of nanofacets fabricated at different time scales, under low energy ion impacts, yield tunable field emission with a Fowler-Nordheim tunneling field in the range of 0.67-4.75 V μm -1 . The local probe surface microscopy-based tunneling current mapping in conjunction with Kelvin probe force microscopy measurements revealed that the valleys and a part of the sidewalls of the nanofacets contribute more to the field emission process. The observed lowest turn-on field is attributed to the absence of native oxide on the sidewalls of the smallest facets as well as their lowest work function. In addition, first-principle density functional theory-based simulation revealed a crystal orientation-dependent work function of Si, which corroborates well with our experimental observations. The present study demonstrates a novel way to address the origin of the cold cathode electron emission sites from Si-NFs fabricated at room temperature. In principle, the present methodology can be extended to probe the cold cathode electron emission sites from any nanostructured material.

Eye-Safe Polycrystalline Lasers

DTIC Science & Technology

2013-03-01

developed novel ceramic and single crystal laser gain media as a platform for power scaling to +100 kW class levels. Hydrothermal techniques were used...order of magnitude improvement in purity. Bulk single crystal growth was demonstrated for scandia and lutetia single crystals , as well as several...exhibited equivalent transparency to that of the single crystal in the near-infrared spectral region and initial lasing results have been successful

Single crystalline hollow metal-organic frameworks: a metal-organic polyhedron single crystal as a sacrificial template.

PubMed

Kim, Hyehyun; Oh, Minhak; Kim, Dongwook; Park, Jeongin; Seong, Junmo; Kwak, Sang Kyu; Lah, Myoung Soo

2015-02-28

Single crystalline hollow metal-organic frameworks (MOFs) with cavity dimensions on the order of several micrometers and hundreds of micrometers were prepared using a metal-organic polyhedron single crystal as a sacrificial hard template. The hollow nature of the MOF crystal was confirmed by scanning electron microscopy of the crystal sliced using a focused ion beam.

Crystal growth, structure analysis and characterisation of 2 - (1, 3 - dioxoisoindolin - 2 - yl) acetic acid single crystal

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

Sankari, R. Siva, E-mail: sivasankari.sh@act.edu.in; Perumal, Rajesh Narayana

2014-04-24

Single crystal of dielectric material 2 - (1, 3 - dioxoisoindolin - 2 - yl) acetic acid has been grown by slow evaporation solution growth method. The grown crystal was harvested in 25 days. The crystal structure was analyzed by Single crystal X - ray diffraction. UV-vis-NIR analysis was performed to examine the optical property of the grown crystal. The thermal property of the grown crystal was studied by thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The dielectric measurements were carried out and the dielectric constant was calculated and plotted at all frequencies.

Single-Cylinder Oil-Control Tests of Porous Chrome-Plated Cylinder Barrels for Radial Air-Cooled Engines

DTIC Science & Technology

1946-01-01

plating, it will affect a choke as desired in the cylinder. When the clearance between the anode and the cathode (cylinder barrel) is decreased, an...National Advisory Commltteo for Aeronautics, Cltivel« oid , Ohio. RSFEFKICE3 1. Johnson, Robert L., wad Anderson, Roy I.: S.’.nglo-Cylindor Engine Tests...plating a choke in the bore. Choice la obtained by decreasing the clear- ance between the anode and the cylinder barrel ( cathode ). Taper on anode la

Wafer-scale single-crystal perovskite patterned thin films based on geometrically-confined lateral crystal growth

PubMed Central

Lee, Lynn; Baek, Jangmi; Park, Kyung Sun; Lee, Yong-EunKoo; Shrestha, Nabeen K.; Sung, Myung M.

2017-01-01

We report a facile roll-printing method, geometrically confined lateral crystal growth, for the fabrication of large-scale, single-crystal CH3NH3PbI3 perovskite thin films. Geometrically confined lateral crystal growth is based on transfer of a perovskite ink solution via a patterned rolling mould to a heated substrate, where the solution crystallizes instantly with the immediate evaporation of the solvent. The striking feature of this method is that the instant crystallization of the feeding solution under geometrical confinement leads to the unidirectional lateral growth of single-crystal perovskites. Here, we fabricated single-crystal perovskites in the form of a patterned thin film (3 × 3 inch) with a high carrier mobility of 45.64 cm2 V−1 s−1. We also used these single-crystal perovskite thin films to construct solar cells with a lateral configuration. Their active-area power conversion efficiency shows a highest value of 4.83%, which exceeds the literature efficiency values of lateral perovskite solar cells. PMID:28691697

Mosaic anisotropy model for magnetic interactions in mesostructured crystals

NASA Astrophysics Data System (ADS)

Goldman, Abby R.; Asenath-Smith, Emily; Estroff, Lara A.

2017-10-01

We propose a new model for interpreting the magnetic interactions in crystals with mosaic texture called the mosaic anisotropy (MA) model. We test the MA model using hematite as a model system, comparing mosaic crystals to polycrystals, single crystal nanoparticles, and bulk single crystals. Vibrating sample magnetometry confirms the hypothesis of the MA model that mosaic crystals have larger remanence (Mr/Ms) and coercivity (Hc) compared to polycrystalline or bulk single crystals. By exploring the magnetic properties of mesostructured crystalline materials, we may be able to develop new routes to engineering harder magnets.

New Rhenium-Doped SrCo1−xRexO3−δ Perovskites Performing as Cathodes in Solid Oxide Fuel Cells

PubMed Central

Troncoso, Loreto; Gardey, María Celeste; Fernández-Díaz, María Teresa; Alonso, José Antonio

2016-01-01

In the aim to stabilize novel three-dimensional perovskite oxides based upon SrCoO3−δ, we have designed and prepared SrCo1−xRexO3−δ phases (x = 0.05 and 0.10), successfully avoiding the competitive hexagonal 2H polytypes. Their performance as cathode materials in intermediate-temperature solid oxide fuel cells (IT-SOFC) has been investigated. The characterization of these oxides included X-ray (XRD) and in situ temperature-dependent neutron powder diffraction (NPD) experiments for x = 0.10. At room temperature, SrCo1−xRexO3−δ perovskites are defined in the P4/mmm space group, which corresponds to a subtle tetragonal perovskite superstructure with unit-cell parameters a = b ≈ ao, c = 2ao (ao = 3.861 and 3.868 Å, for x = 0.05 and 0.10, respectively). The crystal structure evolves above 380 °C to a simple cubic perovskite unit cell, as observed from in-situ NPD data. The electrical conductivity gave maximum values of 43.5 S·cm−1 and 51.6 S·cm−1 for x = 0.05 and x = 0.10, respectively, at 850 °C. The area specific resistance (ASR) polarization resistance determined in symmetrical cells is as low as 0.087 Ω·cm2 and 0.065 Ω·cm2 for x = 0.05 and x = 0.10, respectively, at 850 °C. In single test cells these materials generated a maximum power of around 0.6 W/cm2 at 850 °C with pure H2 as a fuel, in an electrolyte-supported configuration with La0.8Sr0.2Ga0.83Mg0.17O3−δ (LSGM) as the electrolyte. Therefore, we propose the SrCo1−xRexO3−δ (x = 0.10 and 0.05) perovskite oxides as promising candidates for cathodes in IT-SOFC. PMID:28773844

Three-Dimensional Transport Modeling for Proton Exchange Membrane(PEM) Fuel Cell with Micro Parallel Flow Field

PubMed Central

Lee, Pil Hyong; Han, Sang Seok; Hwang, Sang Soon

2008-01-01

Modeling and simulation for heat and mass transport in micro channel are being used extensively in researches and industrial applications to gain better understanding of the fundamental processes and to optimize fuel cell designs before building a prototype for engineering application. In this study, we used a single-phase, fully three dimensional simulation model for PEMFC that can deal with both anode and cathode flow field for examining the micro flow channel with electrochemical reaction. The results show that hydrogen and oxygen were solely supplied to the membrane by diffusion mechanism rather than convection transport, and the higher pressure drop at cathode side is thought to be caused by higher flow rate of oxygen at cathode. And it is found that the amount of water in cathode channel was determined by water formation due to electrochemical reaction plus electro-osmotic mass flux directing toward the cathode side. And it is very important to model the back diffusion and electro-osmotic mass flux accurately since the two flux was closely correlated each other and greatly influenced for determination of ionic conductivity of the membrane which directly affects the performance of fuel cell. PMID:27879774

Activity and Stability of (Pr 1-xNd x) 2NiO 4 as Cathodes for Solid Oxide Fuel Cells: II. Electrochemical Performance and Performance Durability

DOE PAGES

Dogdibegovic, Emir; Guan, Wanbing; Yan, Jingbo; ...

2016-09-21

Single phase (Pr 1-xNd x) 2NiO 4 cathode powders (x = 0, 0.25, 0.50, 0.75, and 1.0) were synthesized via a glycine-nitrate combustion and high temperature calcination. Anode supported cells were used to investigate the cathode property. A reproducible performance, within 9% for each cathode composition, was observed providing a wealth of data for quantitative studies. Area specific resistance analysis and i-V measurements between 650 and 850°C showed a decrease in the cell performance with increasing Nd content. Impedance spectrum analysis suggests that the decline in performance results from an increase in electrode polarization. While Pr 2NiO 4 cells showedmore » significant performance degradation of 6.40%/1,000 hours, the degradation rate for (Pr 0.75Nd 0.25) 2NiO 4 cells was reduced by an order of magnitude (0.56%/1,000 hours) with a 7% lower power output. Furthermore, the cathodes with a higher Nd content showed further improvement in performance stability with a marginal degradation rate of 0.06%/1,000 hours.« less

Multiday Transcranial Direct Current Stimulation Causes Clinically Insignificant Changes in Childhood Dystonia: A Pilot Study.

PubMed

Bhanpuri, Nasir H; Bertucco, Matteo; Young, Scott J; Lee, Annie A; Sanger, Terence D

2015-10-01

Abnormal motor cortex activity is common in dystonia. Cathodal transcranial direct current stimulation may alter cortical activity by decreasing excitability while anodal stimulation may increase motor learning. Previous results showed that a single session of cathodal transcranial direct current stimulation can improve symptoms in childhood dystonia. Here we performed a 5-day, sham-controlled, double-blind, crossover study, where we measured tracking and muscle overflow in a myocontrol-based task. We applied cathodal and anodal transcranial direct current stimulation (2 mA, 9 minutes per day). For cathodal transcranial direct current stimulation (7 participants), 3 subjects showed improvements whereas 2 showed worsening in overflow or tracking error. The effect size was small (about 1% of maximum voluntary contraction) and not clinically meaningful. For anodal transcranial direct current stimulation (6 participants), none showed improvement, whereas 5 showed worsening. Thus, multiday cathodal transcranial direct current stimulation reduced symptoms in some children but not to a clinically meaningful extent, whereas anodal transcranial direct current stimulation worsened symptoms. Our results do not support transcranial direct current stimulation as clinically viable for treating childhood dystonia. © The Author(s) 2015.

Experimental study of humidity changes on the performance of an elliptical single four-channel PEM fuel cell

NASA Astrophysics Data System (ADS)

Gholizadeh, Mohammad; Ghazikhani, Mohsen; Khazaee, Iman

2017-01-01

Humidity and humidification in a proton exchange membrane fuel cells (PEM) can significantly affect the performance of these energy generating devices. Since protons (H+) needs to be accompanied by water molecules to pass from the anode side to the cathode side, the PEM fuel cell membrane should be sufficiently wet. Low or high amount of water in the membrane can interrupt the flow of protons and thus reduce the efficiency of the fuel cell. In this context, several experimental studies and modeling have been carried out on PEM fuel cell and interesting results have been achieved. In this paper, the humidity and flow rate of gas in the anode and cathode are modified to examine its effect on fuel cell performance. The results show that the effect of humidity changing in the anode side is greater than that of the cathode so that at zero humidity of anode and 70 % humidity of the cathode, a maximum current flow of 0.512 A/cm2 for 0.12 V was obtained. However, at 70 % anode humidity and zero cathode humidity, a maximum flow of 0.86 A/cm2 for 0.13 V was obtained.

SPECTROSOCPIC STUDIES OF IONIZATION IN A HOLLOW-CATHODE DISCHARGE

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

Mitchell, K.B.

1961-08-01

The influence of carrier gas, carrier gas pressure, cathode geometry, and discharge current on the ionization of metal atoms in a hollow-cathode discharge was studied in some detail. Most of these studies were raade with an iron hollowcathode discharge. A measure of ionization was obtained from the intensity ratio of a line of the second to a line of the first spectrum. In general, this ratio was found to increase with carrier gas pressure and discharge current. This ratio also increased with increasing cathode bcre diameter but decreased with increasing bcre length. This ratio for iron was greatly affected bymore » the use of different inert carrier gases. Of the five common inert gases used, xenon produced the largest value for this ratio and argon produced the smallest. The results of these studies indicated this may be a new method for distinguishing between lines emitted by the neutral atom and lines of the singly ionized atom. (auth)« less

La(0.4)Ba(0.6)Fe(0.8)Zn(0.2)O(3-delta) as cathode in solid oxide fuel cells for simultaneous NO reduction and electricity generation.

PubMed

Zhou, Renjie; Bu, Yunfei; Xu, Dandan; Zhong, Qin

2014-01-01

A perovskite-type oxide La(0.4)Ba(0.6)Fe(0.8)Zn(0.2)O(3-delta) (LBFZ) was investigated as the cathode material for simultaneous NO reduction and electricity generation in solid oxide fuel cells (SOFCs). The microstructure of LBFZ was demonstrated by X-ray diffraction and scanning electron microscopy. The results showed that a single cubic perovskite LBFZ was formed after calcined at 1100 degrees C. Meanwhile, the solid-state reaction between LBFZ and Ce(0.8)Sm(0.2)O(1.9) (SDC) at 900 degrees C was negligible. To measure the electrochemical properties, SOFC units were constructed with Sm(0.9)Sr(0.1)Cr(0.5)Fe(0.5)O3 as the anode, SDC as the electrolyte and LBFZ as the cathode. The maximum power density increased with the increasing NO concentration and temperature. The cell resistance is mainly due to the cathodic polarization resistance.

Patterned solid state growth of barium titanate crystals

NASA Astrophysics Data System (ADS)

Ugorek, Michael Stephen

An understanding of microstructure evolution in ceramic materials, including single crystal development and abnormal/enhanced grain growth should enable more controlled final ceramic element structures. In this study, two different approaches were used to control single crystal development in a patterned array. These two methods are: (1) patterned solid state growth in BaTiO 3 ceramics, and (2) metal-mediated single crystal growth in BaTiO 3. With the patterned solid state growth technique, optical photolithography was used to pattern dopants as well as [001] and [110] BaTiO3 single crystal template arrays with a 1000 microm line pattern array with 1000 microm spacings. These patterns were subsequently used to control the matrix grain growth evolution and single crystal development in BaTiO3. It was shown that the growth kinetics can be controlled by a small initial grain size, atmosphere conditions, and the introduction of a dopant at selective areas/interfaces. By using a PO2 of 1x10-5 atm during high temperature heat treatment, the matrix coarsening has been limited (to roughly 2 times the initial grain size), while retaining single crystal boundary motion up to 0.5 mm during growth for dwell times up to 9 h at 1300°C. The longitudinal and lateral growth rates were optimized at 10--15 microm/h at 1300°C in a PO2 of 1x10 -5 atm for single crystal growth with limited matrix coarsening. Using these conditions, a patterned microstructure in BaTiO3 was obtained. With the metal-mediated single crystal growth technique, a novel approach for fabricating 2-2 single crystal/polymer composites with a kerf < 5 microns was demonstrated. Surface templated grain growth was used to propagate a single crystal interface into a polycrystalline BaTiO3 or Ba(Zr0.05 Ti0.95)O3 matrix with lamellar nickel layers. The grain growth evolution and texture development were studied using both [001] and [110] BaTiO3 single crystals templates. By using a PO 2 of 1x10-11 atm during high temperature heat treatment, matrix coarsening was limited while enabling single crystal boundary motion up to 0.35 mm during growth between 1250°C and 1300°C with growth rates ˜ 3--4 microm/h for both single crystal orientations. By removing the inner electrodes, 2-2 single crystal (or ceramic) composites were prepared. The piezoelectric and dielectric properties of the composites of the two compositions were measured. The d33 and d31 of the composites were similar to the polycrystalline ceramic of the same composition.

The evolution of machining-induced surface of single-crystal FCC copper via nanoindentation

NASA Astrophysics Data System (ADS)

Zhang, Lin; Huang, Hu; Zhao, Hongwei; Ma, Zhichao; Yang, Yihan; Hu, Xiaoli

2013-05-01

The physical properties of the machining-induced new surface depend on the performance of the initial defect surface and deformed layer in the subsurface of the bulk material. In this paper, three-dimensional molecular dynamics simulations of nanoindentation are preformed on the single-point diamond turning surface of single-crystal copper comparing with that of pristine single-crystal face-centered cubic copper. The simulation results indicate that the nucleation of dislocations in the nanoindentation test on the machining-induced surface and pristine single-crystal copper is different. The dislocation embryos are gradually developed from the sites of homogeneous random nucleation around the indenter in the pristine single-crystal specimen, while the dislocation embryos derived from the vacancy-related defects are distributed in the damage layer of the subsurface beneath the machining-induced surface. The results show that the hardness of the machining-induced surface is softer than that of pristine single-crystal copper. Then, the nanocutting simulations are performed along different crystal orientations on the same crystal surface. It is shown that the crystal orientation directly influences the dislocation formation and distribution of the machining-induced surface. The crystal orientation of nanocutting is further verified to affect both residual defect generations and their propagation directions which are important in assessing the change of mechanical properties, such as hardness and Young's modulus, after nanocutting process.

Electron paramagnetic resonance study of radiation-induced paramagnetic centers in succinic anhydride single crystal

NASA Astrophysics Data System (ADS)

Caliskan, Betul; Caliskan, Ali Cengiz; Er, Emine

2017-09-01

Succinic anhydride single crystals were exposed to 60Co-gamma irradiation at room temperature. The irradiated single crystals were investigated at 125 K by Electron Paramagnetic Resonance (EPR) Spectroscopy. The investigation of EPR spectra of irradiated single crystals of succinic anhydride showed the presence of two succinic anhydride anion radicals. The anion radicals observed in gamma-irradiated succinic anhydride single crystal were created by the scission of the carbon-oxygen double bond. The structure of EPR spectra demonstrated that the hyperfine splittings arise from the same radical species. The reduction of succinic anhydride was identified which is formed by the addition of an electron to oxygen of the Csbnd O bond. The g values, the hyperfine structure constants and direction cosines of the radiation damage centers observed in succinic anhydride single crystal were obtained.

Study of structural and optical properties of YAG and Nd:YAG single crystals

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

Kostić, S.; Lazarević, Z.Ž., E-mail: lzorica@yahoo.com; Radojević, V.

2015-03-15

Highlights: • Transparent YAG and pale pink Nd:YAG single crystals were produced by the Czochralski technique. • Growth mechanisms and shape of the liquid/solid interface and incorporation of Nd{sup 3+} were studied. • The structure of the crystals was investigated by X-ray diffraction, Raman and IR spectroscopy. • The 15 Raman and 17 IR modes were observed. • The obtained YAG and Nd:YAG single crystals were without core and of good optical quality. - Abstract: Yttrium aluminum garnet (YAG, Y{sub 3}Al{sub 5}O{sub 12}) and yttrium aluminum garnet doped with neodymium (Nd:YAG) single crystals were grown by the Czochralski technique. Themore » critical diameter and the critical rate of rotation were calculated. Suitable polishing and etching solutions were determined. As a result of our experiments, the transparent YAG and pale pink Nd:YAG single crystals were produced. The obtained crystals were studied by X-ray diffraction, Raman and IR spectroscopy. The crystal structure was confirmed by XRD. The 15 Raman and 17 IR modes were observed. The Raman and IR spectroscopy results are in accordance with X-ray diffraction analysis. The obtained YAG and Nd:YAG single crystals were without core and of good optical quality. The absence of a core was confirmed by viewing polished crystal slices. Also, it is important to emphasize that the obtained Nd:YAG single crystal has a concentration of 0.8 wt.% Nd{sup 3+} that is characteristic for laser materials.« less

Structural, optical, mechanical and dielectric studies of pure and doped L-Prolinium trichloroacetate single crystals.

PubMed

Renuka, N; Ramesh Babu, R; Vijayan, N; Vasanthakumar, Geetha; Krishna, Anuj; Ramamurthi, K

2015-02-25

In the present work, pure and metal substituted L-Prolinium trichloroacetate (LPTCA) single crystals were grown by slow evaporation method. The grown crystals were subjected to single crystal X-ray diffraction (XRD), powder X-ray diffraction, FTIR, UV-Visible-NIR, hardness, photoluminescence and dielectric studies. The dopant concentration in the crystals was measured by inductively coupled plasma (ICP) analysis. Single crystal X-ray diffraction studies of the pure and metal substituted LPTCA revealed that the grown crystals belong to the trigonal system. Ni(2+) and Co(2+) doping slightly altered the lattice parameters of LPTCA without affecting the basic structure of the crystal. FTIR spectral analysis confirms the presence of various functional groups in the grown crystals. The mechanical behavior of pure and doped crystals was analyzed by Vickers's microhardness test. The optical transmittance, dielectric and photoluminescence properties of the pure and doped crystals were analyzed. Copyright © 2014 Elsevier B.V. All rights reserved.

Single crystals of selected titanates and tungstates

NASA Technical Reports Server (NTRS)

Loiacono, G. M.

1972-01-01

The compound preparation and crystal growth of a number of mixed titanate compositions was investigated. None of the compounds studied were found to melt congruently and therefore, crystal growth was extremely difficult. Various single crystal preparation methods always resulted in mixed phases from which 1-2 mm size crystals could be separated. It is concluded from this study that before successful single crystal growth can be accomplished, a detailed study of the phase diagrams in each of the systems of interest must be completed.

Interface Character of Aluminum-Graphite Metal Matrix Composites.

DTIC Science & Technology

1983-01-27

studied included the commer- cial A/graphite composites; layered model systems on single crystal and poly- crystalline graphite substrates as well as...composition and thickness of the composite interface, and graphite crystal orientation. 3 For the model systems in this study , single crystal graphite...been reviewed by Kingcry. Segregation at surfaces in single- crystal MgO of Fe, Cr and Sc, which were Dresent in concentrations within the single- 3phase

Magnetic and magnetostrictive behavior of Dy 3+ doped CoFe 2O 4 single crystals grown by flux method

NASA Astrophysics Data System (ADS)

Kambale, Rahul C.; Song, K. M.; Won, C. J.; Lee, K. D.; Hur, N.

2012-02-01

We studied the effect of Dy 3+ content on the magnetic properties of cobalt ferrite single crystal. The single crystals of CoFe 1.9Dy 0.1O 4 were grown by the flux method using Na 2B 4O 7.10 H 2O (Borax) as a solvent (flux). The black and shiny single crystals were obtained as a product. The X-ray diffraction analysis at room temperature confirmed the spinel cubic structure with lattice constant a=8.42 Å of the single crystals. The compositional analysis endorses the presence of constituents Co, Fe and Dy elements after sintering at 1300 °C within the final structure. The magnetic hysteresis measurements at various temperatures viz. 10 K, 100 K, 200 K and 300 K reveal the soft ferrimagnetic nature of the single crystal than that of for pure CoFe 2O 4. The observed saturation magnetization ( Ms) and coercivity ( Hc) are found to be lower than that of pure CoFe 2O 4 single crystal. The magnetostriction ( λ) measurement was carried out along the [001] direction. The magnetic measurements lead to conclude that the present single crystals can be used for magneto-optic recording media.

Magnetic spherical cores partly coated with periodic mesoporous organosilica single crystals.

PubMed

Li, Jing; Wei, Yong; Li, Wei; Deng, Yonghui; Zhao, Dongyuan

2012-03-07

Core-shell structured materials are of special significance in various applications. Until now, most reported core-shell structures have polycrystalline or amorphous coatings as their shell layers, with popular morphologies of microspheres or quasi-spheres. However, the single crystals, either mesoscale or atomic ones, are still rarely reported as shell layers. If single crystals can be coated on core materials, it would result in a range of new type core-shell structures with various morphologies, and probably more potential applications. In this work, we demonstrate that periodic mesoporous organosilica (PMO) single crystals can partly grow on magnetic microspheres to form incomplete Fe(3)O(4)@nSiO(2)@PMO core-shell materials in aqueous solution, which indeed is the first illustration that mesoporous single-crystal materials can be used as shell layers for preparation of core-shell materials. The achieved materials have advantages of high specific surface areas, good magnetic responses, embedded functional groups and cubic mesopore channels, which might provide them with various application conveniences. We suppose the partial growth is largely decided by the competition between growing tendency of single crystals and the resistances to this tendency. In principle, other single crystals, including a range of atomic single crystals, such as zeolites, are able to be developed into such core-shell structures.

Flux growth of high-quality CoFe 2O 4 single crystals and their characterization

NASA Astrophysics Data System (ADS)

Wang, W. H.; Ren, X.

2006-04-01

We report the growth of high-quality CoFe 2O 4 single crystals using a borax flux method. The crystals were characterized by powder X-ray diffraction, electron probe microanalysis and Raman spectroscopy. We found the crystals are flux-free and highly homogeneous in composition. X-ray rocking curves of the CoFe 2O 4 single crystals showed a full-width at half-maximum of 0.15°. The saturation magnetization of the CoFe 2O 4 single crystals was measured to be 90 emu/g or equivalently 3.65 μ B/f.u. at 5 K.

Polymer-Templated LiFePO4/C Nanonetworks as High-Performance Cathode Materials for Lithium-Ion Batteries.

PubMed

Fischer, Michael G; Hua, Xiao; Wilts, Bodo D; Castillo-Martínez, Elizabeth; Steiner, Ullrich

2018-01-17

Lithium iron phosphate (LFP) is currently one of the main cathode materials used in lithium-ion batteries due to its safety, relatively low cost, and exceptional cycle life. To overcome its poor ionic and electrical conductivities, LFP is often nanostructured, and its surface is coated with conductive carbon (LFP/C). Here, we demonstrate a sol-gel based synthesis procedure that utilizes a block copolymer (BCP) as a templating agent and a homopolymer as an additional carbon source. The high-molecular-weight BCP produces self-assembled aggregates with the precursor-sol on the 10 nm scale, stabilizing the LFP structure during crystallization at high temperatures. This results in a LFP nanonetwork consisting of interconnected ∼10 nm-sized particles covered by a uniform carbon coating that displays a high rate performance and an excellent cycle life. Our "one-pot" method is facile and scalable for use in established battery production methodologies.

Effects of neutron and gamma radiation on lithium-ion batteries

NASA Astrophysics Data System (ADS)

Qiu, Jie; He, Dandan; Sun, Mingzhai; Li, Shimeng; Wen, Cun; Hattrick-Simpers, Jason; Zheng, Yuan F.; Cao, Lei

2015-02-01

Radiation induced deterioration in the performance of lithium-ion (Li-ion) batteries can result in functional failures of electronic devices in modern electronic systems. The stability of the Li-ion battery under a radiation environment is of crucial importance. In this work, the surface morphology of the cathode material of a commercial Li-ion battery before and after neutron and gamma ray irradiation was characterized by atomic force microscopy (AFM). We found growth in the particle size of the cathode material in the range of 36-45% as a result of the irradiation. In addition, X-ray diffraction (XRD) patterns revealed a disordering of the crystal structure occurring in the post-irradiation sample. All of these led to a 8.4% capacity loss of the battery for the maximum received irradiation dose (2.744 Mrad) at post-irradiation. The effects of the radiation on the Li-ion battery are discussed in this paper.

Air-cathode microbial fuel cell array: a device for identifying and characterizing electrochemically active microbes.

PubMed

Hou, Huijie; Li, Lei; de Figueiredo, Paul; Han, Arum

2011-01-15

Microbial fuel cells (MFCs) have generated excitement in environmental and bioenergy communities due to their potential for coupling wastewater treatment with energy generation and powering diverse devices. The pursuit of strategies such as improving microbial cultivation practices and optimizing MFC devices has increased power generating capacities of MFCs. However, surprisingly few microbial species with electrochemical activity in MFCs have been identified because current devices do not support parallel analyses or high throughput screening. We have recently demonstrated the feasibility of using advanced microfabrication methods to fabricate an MFC microarray. Here, we extend these studies by demonstrating a microfabricated air-cathode MFC array system. The system contains 24 individual air-cathode MFCs integrated onto a single chip. The device enables the direct and parallel comparison of different microbes loaded onto the array. Environmental samples were used to validate the utility of the air-cathode MFC array system and two previously identified isolates, 7Ca (Shewanella sp.) and 3C (Arthrobacter sp.), were shown to display enhanced electrochemical activities of 2.69 mW/m(2) and 1.86 mW/m(2), respectively. Experiments using a large scale conventional air-cathode MFC validated these findings. The parallel air-cathode MFC array system demonstrated here is expected to promote and accelerate the discovery and characterization of electrochemically active microbes. Copyright © 2010 Elsevier B.V. All rights reserved.

EPR study of free radical in gamma-irradiated bis(cyclopentadienyl)zirconium dichloride single crystal

NASA Astrophysics Data System (ADS)

Caliskan, Betul; Caliskan, Ali Cengiz

2017-06-01

Bis(cyclopentadienyl)zirconium dichloride (BCZD; zirconocene dichloride) single crystals were exposed to 60Co-γ irradiation at room temperature. The irradiated single crystals were investigated between 125 and 470 K by electron paramagnetic resonance spectroscopy. The spectra of the crystals were found to be temperature independent. The paramagnetic center was attributed to the cyclopentadienyl radical. The g values of the radiation damage center observed in BCZD single crystal and the hyperfine structure constants of the free electron with nearby protons were obtained.

Growth and characterization of CaCu3Ti4O12 single crystals

NASA Astrophysics Data System (ADS)

Kim, Hui Eun; Yang, Sang-don; Lee, Jung-Woo; Park, Hyun Min; Yoo, Sang-Im

2014-12-01

The CaCu3Ti4O12 (CCTO) single crystals could be grown from the melt with the nominal composition of Ca:Cu:Ti=1:59:20 in a platinum (Pt) crucible using a self-flux method. The flux-grown CCTO single crystals have well-developed {100} habit planes, and their compositions are close to the ratio of Ca:Cu:Ti=1:3:4. Interestingly, flux-grown CCTO single crystals exhibited two different back reflection Laue patterns; one exhibited only [100] cubic Laue patterns, and the other showed not only [100] cubic Laue patterns but also the satellite spots related to the twin boundary, implying that twin-free CCTO single crystals can be grown by the self-flux method. Both the dielectric constants and losses of twinned CCTO single crystal are significantly higher than those of untwined CCTO crystal at relatively low frequency regime (<10 kHz), suggesting that the dielectric property is sensitive to the twin boundary.

A multistep single-crystal-to-single-crystal bromodiacetylene dimerization

NASA Astrophysics Data System (ADS)

Hoheisel, Tobias N.; Schrettl, Stephen; Marty, Roman; Todorova, Tanya K.; Corminboeuf, Clémence; Sienkiewicz, Andrzej; Scopelliti, Rosario; Schweizer, W. Bernd; Frauenrath, Holger

2013-04-01

Packing constraints and precise placement of functional groups are the reason that organic molecules in the crystalline state often display unusual physical or chemical properties not observed in solution. Here we report a single-crystal-to-single-crystal dimerization of a bromodiacetylene that involves unusually large atom displacements as well as the cleavage and formation of several bonds. Density functional theory computations support a mechanism in which the dimerization is initiated by a [2 + 1] photocycloaddition favoured by the nature of carbon-carbon short contacts in the crystal structure. The reaction proceeded up to the theoretical degree of conversion without loss of crystallinity, and it was also performed on a preparative scale with good yield. Moreover, it represents the first synthetic pathway to (E)-1,2-dibromo-1,2-diethynylethenes, which could serve as synthetic intermediates for the preparation of molecular carbon scaffolds. Our findings both extend the scope of single-crystal-to-single-crystal reactions and highlight their potential as a synthetic tool for complex transformations.

Preparation of Gd(OH){sub 3} large single crystals by solid KOH assisted hydrothermal method and their luminescent and magnetic properties

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

Wu, Hai; Zhang, Youjin, E-mail: zyj@ustc.edu.cn; Zhou, Maozhong

Highlights: • Gd(OH){sub 3} large single crystals were prepared by solid KOH assisted hydrothermal method. • The possible growth mechanism of Gd(OH){sub 3} large single crystals was proposed. • The Gd(OH){sub 3} samples emitted a strong narrow-band ultraviolet B (NB-UVB) light. • The Gd(OH){sub 3} samples showed good paramagnetic properties. - Abstract: Large single crystals of gadolinium hydroxide [Gd(OH){sub 3}] in the length of several millimeters were successfully prepared by using solid KOH assisted hydrothermal method. Gd(OH){sub 3} samples were characterized by X-ray diffraction (XRD), 4-circle single-crystal diffraction, Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). FESEM imagemore » shows hexagonal prism morphology for the Gd(OH){sub 3} large crystals. The possible growth mechanism of Gd(OH){sub 3} large single crystals was proposed. The photoluminescence and magnetic properties of Gd(OH){sub 3} species were investigated.« less

Method for the growth of large low-defect single crystals

NASA Technical Reports Server (NTRS)

Powell, J. Anthony (Inventor); Neudeck, Philip G. (Inventor); Trunek, Andrew J. (Inventor); Spry, David J. (Inventor)

2008-01-01

A method and the benefits resulting from the product thereof are disclosed for the growth of large, low-defect single-crystals of tetrahedrally-bonded crystal materials. The process utilizes a uniquely designed crystal shape whereby the direction of rapid growth is parallel to a preferred crystal direction. By establishing several regions of growth, a large single crystal that is largely defect-free can be grown at high growth rates. This process is particularly suitable for producing products for wide-bandgap semiconductors, such as SiC, GaN, AlN, and diamond. Large low-defect single crystals of these semiconductors enable greatly enhanced performance and reliability for applications involving high power, high voltage, and/or high temperature operating conditions.

Crystalline perfection and optical studies of L-Histidinium dihydrogen phosphate orthophosphoric acid (LHDP) single crystals

NASA Astrophysics Data System (ADS)

Ittyachan, Reena; Arunkumar, A.; Bhagavannarayana, G.

2015-10-01

Single crystals of L-Histidinium dihydrogenphosphate orthophosphoric acid (LHDP) were grown by slow evaporation solution growth technique. The grown crystals were confirmed by single crystal X-ray diffraction techniques. The HRXRD rocking curve measurements revealed the crystalline perfection of grown crystal and the absence of structural grain boundaries. The lower optical cut-off wavelength for this crystal was observed at 240 nm. The third order nonlinear refractive index (n2), nonlinear absorption coefficient (β) and susceptibility (χ(3)) were calculated by Z-scan studies using Nd: YAG laser as a source. The single shot laser damage threshold of grown crystal was measured to be 6.286 GW/cm2 using Nd: YAG laser.

Synthesis, crystal structure, thermal and nonlinear optical properties of new metal-organic single crystal: Tetrabromo (piperazinium) zincate (II) (TBPZ)

NASA Astrophysics Data System (ADS)

Boopathi, K.; Babu, S. Moorthy; Ramasamy, P.

2018-04-01

Tetrabromo (piperazinium) zincate, a new metal-organic crystal has been synthesized and its single crystal grown by slow evaporation method. The grown crystal has characterized by structural, spectral, thermal, linear and nonlinear optical properties. Single crystal X-ray diffractions study reveals that grown crystal belongs to orthorhombic crystal system with space group P212121. The presence of functional groups is identified by FT-IR spectral analysis. Thermal stability of the crystal was ascertained by TG-DTA measurement. The second order harmonic generation efficiency was measured using Kurtz and Perry technique and it was found to be 1.5 times that of KDP.

High performance planar p-i-n perovskite solar cells with crown-ether functionalized fullerene and LiF as double cathode buffer layers

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

Liu, Xiaodong; Zhou, Yi, E-mail: yizhou@suda.edu.cn, E-mail: songbo@suda.edu.cn, E-mail: liyf@iccas.ac.cn; Song, Bo, E-mail: yizhou@suda.edu.cn, E-mail: songbo@suda.edu.cn, E-mail: liyf@iccas.ac.cn

2015-08-10

Double cathode buffer layers (CBLs) composed of fullerene derivative functionalized with a crown-ether end group in its side chain (denoted as PCBC) and a LiF layer were introduced between the PCBM acceptor layer and the top cathode in planar p-i-n perovskite solar cells (pero-SCs) based on CH{sub 3}NH{sub 3}PbI{sub 3−X}Cl{sub X}. The devices with the PCBC/LiF double CBLs showed significant improvements in power conversion efficiency (PCE) and long-term stability when compared to the device with LiF single CBL. Through optimizing the spin-coating speed of PCBC, a maximum PCE of 15.53% has been achieved, which is approximately 15% higher than thatmore » of the device with single LiF CBL. The remarkable improvement in PCE can be attributed to the formation of a better ohmic contact in the CBL between PCBC and LiF/Al electrode arising from the dipole moment of PCBC, leading to the enhanced fill factor and short-circuit current density (J{sub sc}). Besides the PCE, the long-term stability of the devices with PCBC interlayer is also superior to that of the device with LiF single CBL, which is due to the more effective protection for the perovskite/PCBM interface.« less

Performance of NCAP projection displays

NASA Astrophysics Data System (ADS)

Jones, Philip J.; Tomita, Akira; Wartenberg, Mark

1991-08-01

Prototypes of projection displays based on dispersions of liquid crystal in polymer matrices are beginning to appear. The principle of operation depends on electrically switchable light scattering. They are potentially much brighter than current cathode ray tube (CRT) or twisted nematic liquid crystal (TN LC) cell based displays. Comparisons of efficacy and efficiency show this. The contrast and brightness of such displays depend on a combination of the f- number of the projection system and the scattering characteristics of the light valve. Simplified equations can be derived to show these effects. The degree of scattering of current NCAP formulations is sufficient to produce good contrast projection displays, at convenient voltages, that are around three times brighter than TN LC projectors because of the lack of polarizers in the former.

How far could energy transport within a single crystal

NASA Astrophysics Data System (ADS)

Zhang, Yifan; Che, Yanke; Zhao, Jincai; Steve, Granick

Efficient transport of excitation energy over long distance is a vital process in light-harvesting systems and molecular electronics. The energy transfer distance is largely restricted by the probability decay of the exciton when hopping within a single crystal. Here, we fabricated an organic single crystal within which the energy could transfer more than 100 μm, a distance only limited by its crystal size. Our system could be regarded as a ``Sprint relay game'' performing on different surface of tracks. Photoinduced ``athletes'' (excitons) triggered intermolecular ``domino'' reaction to propagate energy for a long distance. In addition, athletes with the same ability runs much farther on smooth ideal track (single crystal assembled from merely van der Waals interaction) than bumpy mud track (crystal assembled from combination of pi-stacking, hydrogen bond and van der Waals interactions). Our finding presents new physics on enhancing energy transfer length within a single crystal. Current Affiliation: Institute for Basic Science, South Korea.

Effect of Crystal Orientation on Fatigue Failure of Single Crystal Nickel Base Turbine Blade Superalloys

NASA Technical Reports Server (NTRS)

Arakere, N. K.; Swanson, G.

2002-01-01

High cycle fatigue (HCF) induced failures in aircraft gas turbine and rocket engine turbopump blades is a pervasive problem. Single crystal nickel turbine blades are being utilized in rocket engine turbopumps and jet engines throughout industry because of their superior creep, stress rupture, melt resistance, and thermomechanical fatigue capabilities over polycrystalline alloys. Currently the most widely used single crystal turbine blade superalloys are PWA 1480/1493, PWA 1484, RENE' N-5 and CMSX-4. These alloys play an important role in commercial, military and space propulsion systems. Single crystal materials have highly orthotropic properties making the position of the crystal lattice relative to the part geometry a significant factor in the overall analysis. The failure modes of single crystal turbine blades are complicated to predict due to the material orthotropy and variations in crystal orientations. Fatigue life estimation of single crystal turbine blades represents an important aspect of durability assessment. It is therefore of practical interest to develop effective fatigue failure criteria for single crystal nickel alloys and to investigate the effects of variation of primary and secondary crystal orientation on fatigue life. A fatigue failure criterion based on the maximum shear stress amplitude /Delta(sub tau)(sub max))] on the 24 octahedral and 6 cube slip systems, is presented for single crystal nickel superalloys (FCC crystal). This criterion reduces the scatter in uniaxial LCF test data considerably for PWA 1493 at 1200 F in air. Additionally, single crystal turbine blades used in the alternate advanced high-pressure fuel turbopump (AHPFTP/AT) are modeled using a large-scale three-dimensional finite element model. This finite element model is capable of accounting for material orthotrophy and variation in primary and secondary crystal orientation. Effects of variation in crystal orientation on blade stress response are studied based on 297 finite element model runs. Fatigue lives at critical points in the blade are computed using finite element stress results and the failure criterion developed. Stress analysis results in the blade attachment region are also presented. Results presented demonstrates that control of secondary and primary crystallographic orientation has the potential to significantly increase a component S resistance to fatigue crack growth with- out adding additional weight or cost. [DOI: 10.1115/1.1413767

Preparation and guest-uptake protocol for a porous complex useful for 'crystal-free' crystallography.

PubMed

Inokuma, Yasuhide; Yoshioka, Shota; Ariyoshi, Junko; Arai, Tatsuhiko; Fujita, Makoto

2014-02-01

We recently reported a new method for single-crystal X-ray diffraction (SCD) analysis that does not require the crystallization of the target compound. In this 'crystal-free' crystallography, a tiny crystal of a porous complex is soaked in the solution of the target guest. The guest molecules are absorbed and oriented in the crystal pores and can be analyzed by X-ray diffraction. We describe here a detailed synthetic protocol for the preparation of uniform single crystals of the porous host complex and for the subsequent guest uptake. The protocol describes our most versatile porous complex, which is prepared from commercially available ZnI2 and 2,4,6-tri(4-pyridyl)-1,3,5-triazine. The host complex has large pores with a cross-section of 8 × 5 Å(2). Single crystals of the complex are grown from layered solutions of the two components. The pores of the as-synthesized complex are filled with nitrobenzene, which is replaced with the inert solvent cyclohexane. This solvent exchange is essential for the rapid and effective inclusion of target compounds. The most crucial and delicate step is the selection of high-quality single crystals from the mixture of crystals of various shapes and sizes. We suggest using the facial indices of the single crystals as a criterion for crystal selection. Single-crystal samples for X-ray analysis can be prepared by immersing the selected crystals in a cyclohexane/dichloromethane solution of target compound. After a very slow evaporation of the solvent, typically over 2 d, the final crystal can be picked and directly subjected to SCD analysis. The protocol can be completed within ∼16 d.

Linear electro-optic properties of relaxor-based ferroelectric 0.24Pb(In1/2Nb1/2)O3-(0.76 − x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 single crystals

PubMed Central

Wu, Fengmin; Yang, Bin; Sun, Enwei; Liu, Gang; Tian, Hao; Cao, Wenwu

2013-01-01

Linear electro-optic properties of 0.24Pb(In1/2Nb1/2)O3-(0.76 − x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 single crystals, with compositions in the rhombohedral, morphotropic phase boundary (MPB) and tetragonal phases, have been investigated. Very large effective electro-optic coefficient γc (204 pm/V) was observed in a crystal with the MPB composition when it is poled along [001]. The rhombohedral phase (x = 0.27 and 0.30) single crystals poled along [111] direction and tetragonal phase (x = 0.39) single crystal poled along [001] direction are in single domain, and their electro-optic coefficients (γc = 76, 94, and 43 pm/V for the crystals with x = 0.27, 0.30, and 0.39, respectively) were found to be much higher than that of traditional electro-optic single crystal LiNbO3 (γc = 19.9 pm/V). The electro-optic coefficients of the single crystal in the rhombohedral phase have excellent temperature stability in the experimental temperature range of 10–40 °C. The half-wave voltage Vπ was calculated to be much lower (less than 1000 V) than that of LiNbO3 single crystal (2800 V). These superior properties make the ternary relaxor-PT single crystals very promising for electro-optic modulation applications. PMID:23922449

Single crystal and optical ceramic multicomponent garnet scintillators: A comparative study

NASA Astrophysics Data System (ADS)

Wu, Yuntao; Luo, Zhaohua; Jiang, Haochuan; Meng, Fang; Koschan, Merry; Melcher, Charles L.

2015-04-01

Multicomponent garnet materials can be made in optical ceramic as well as single crystal form due to their cubic crystal structure. In this work, high-quality Gd3Ga3Al2O12:0.2 at% Ce (GGAG:Ce) single crystal and (Gd,Lu)3Ga3Al2O12:1 at% Ce (GLuGAG:Ce) optical ceramics were fabricated by the Czochralski method and a combination of hot isostatic pressing (HIPing) and annealing treatment, respectively. Under optical and X-ray excitation, the GLuGAG:Ce optical ceramic exhibits a broad Ce3+ transition emission centered at 550 nm, while the emission peak of the GGAG:Ce single crystal is centered at 540 nm. A self-absorption effect in GLuGAG:Ce optical ceramic results in this red-shift of the Ce3+ emission peak compared to that in the GGAG:Ce single crystal. The light yield under 662 keV γ-ray excitation was 45,000±2500 photons/MeV and 48,200±2410 photons/MeV for the GGAG:Ce single crystal and GLuGAG:Ce optical ceramic, respectively. An energy resolution of 7.1% for 662 keV γ-rays was achieved in the GLuGAG:Ce optical ceramic with a Hamamatsu R6231 PMT, which is superior to the value of 7.6% for a GGAG:Ce single crystal. Scintillation decay time measurements under 137Cs irradiation show two exponential decay components of 58 ns (47%) and 504 ns (53%) for the GGAG:Ce single crystal, and 84 ns (76%) and 148 ns (24%) for the GLuGAG:Ce optical ceramic. The afterglow level after X-ray cutoff in the GLuGAG:Ce optical ceramic is at least one order of magnitude lower than in the GGAG:Ce single crystal.

Structural analysis of benzothienobenzothiophene-based soluble organic semiconducting crystals grown by liquid crystal solvent

NASA Astrophysics Data System (ADS)

Shibata, Yosei; Matsuzaki, Tomoya; Ishinabe, Takahiro; Fujikake, Hideo

2018-06-01

In this study, we analyzed organic semiconducting single crystals composed of benzothienobenzothiophene derivatives (2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene, C8-BTBT) grown by nematic-phase liquid crystal (LC) solvent. As a result, we clarified that the crystal b-axis direction of the C8-BTBT single crystals was consistent with the LC alignment direction. By optical evaluation and simulation based on density functional theory, we found that the C8-BTBT single crystals in LC solvent exhibited a novel molecular conformation having alkyl chains oriented toward the b-axis.

Elastic response of (001)-oriented PWA 1480 single crystal - The influence of secondary orientation

NASA Technical Reports Server (NTRS)

Kalluri, Sreeramesh; Abdul-Azis, Ali; Mcgaw, Michael

1991-01-01

The influence of secondary orientation on the elastic response of a zone axis (001)-oriented nickel-base single-crystal superalloy, PWA 1480, was investigated under mechanical loading conditions by applying finite element techniques. Elastic stress analyses were performed with a commercially available finite element code. Secondary orientation of the single-crystal superalloy was offset with respect to the global coordinate system in increments from 0 to 90 deg and stresses developed within the single crystal were determined for each loading condition. The results indicated that the stresses were strongly influenced by the angular offset between the secondary crystal orientation and the global coordinate system. The degree of influence was found to vary with the type of loading condition (mechanical, thermal, or combined) imposed on the single-crystal superalloy.

Method of making single crystal fibers

NASA Technical Reports Server (NTRS)

Westfall, Leonard J. (Inventor)

1990-01-01

Single crystal fibers are made from miniature extruded ceramic feed rods. A decomposable binder is mixed with powders to inform a slurry which is extruded into a small rod which may be sintered, either in air or in vacuum, or it may be used in the extruded and dried condition. A pair of laser beams focuses onto the tip of the rod to melt it thereby forming a liquid portion. A single crystal seed fiber of the same material as the feed rod contacts this liquid portion to establish a zone of liquid material between the feed rod and the single crystal seed fiber. The feed rod and the single crystal feed fiber are moved at a predetermined speed to solidify the molten zone onto the seed fiber while simultaneously melting additional feed rod. In this manner a single crystal fiber is formed from the liquid portion.

Distributed Feedback Laser Based on Single Crystal Perovskite

NASA Astrophysics Data System (ADS)

Sun, Shang; Xiao, Shumin; Song, Qinghai

2017-06-01

We demonstrate a single crystal perovskite based, with grating-structured photoresist on top, highly polarized distributed feedback laser. A lower laser threshold than the Fabry-Perot mode lasers from the same single crystal CH3NH3PbBr3 microplate was obtained. Single crystal CH3NH3PbBr3 microplates was synthesized with one-step solution processed precipitation method. Once the photoresist on top of the microplate was patterned with electron beam, the device was realized. This one-step fabrication process utilized the advantage of single crystal to the greatest extend. The ultra-low defect density in single crystalline microplate offer an opportunity for lower threshold lasing action compare with poly-crystal perovskite films. In the experiment, the lasing action based on the distributed feedback grating design was found with lower threshold and higher intensity than the Fabry-Perot mode lasers supported by the flat facets of the same microplate.

Effect of grain boundary on the field-effect mobility of microrod single crystal organic transistors.

PubMed

Kim, Jaekyun; Kang, Jingu; Cho, Sangho; Yoo, Byungwook; Kim, Yong-Hoon; Park, Sung Kyu

2014-11-01

High-performance microrod single crystal organic transistors based on a p-type 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) semiconductor are fabricated and the effects of grain boundaries on the carrier transport have been investigated. The spin-coating of C8-BTBT and subsequent solvent vapor annealing process enabled the formation of organic single crystals with high aspect ratio in the range of 10 - 20. It was found that the organic field-effect transistors (OFETs) based on these single crystals yield a field-effect mobility and an on/off current ratio of 8.04 cm2/Vs and > 10(5), respectively. However, single crystal OFETs with a kink, in which two single crystals are fused together, exhibited a noticeable drop of field-effect mobility, and we claim that this phenomenon results from the carrier scattering at the grain boundary.

Single crystal diamond membranes for nanoelectronics.

PubMed

Bray, Kerem; Kato, Hiromitsu; Previdi, Rodolfo; Sandstrom, Russell; Ganesan, Kumaravelu; Ogura, Masahiko; Makino, Toshiharu; Yamasaki, Satoshi; Magyar, Andrew P; Toth, Milos; Aharonovich, Igor

2018-02-22

Single crystal, nanoscale diamond membranes are highly sought after for a variety of applications including nanophotonics, nanoelectronics and quantum information science. However, so far, the availability of conductive diamond membranes has remained an unreachable goal. In this work we present a complete nanofabrication methodology for engineering high aspect ratio, electrically active single crystal diamond membranes. The membranes have large lateral directions, exceeding ∼500 × 500 μm 2 and are only several hundreds of nanometers thick. We further realize vertical single crystal p-n junctions made from the diamond membranes that exhibit onset voltages of ∼10 V and a current of several mA. Moreover, we deterministically introduce optically active color centers into the membranes, and demonstrate for the first time a single crystal nanoscale diamond LED. The robust and scalable approach to engineer the electrically active single crystal diamond membranes offers new pathways for advanced nanophotonic, nanoelectronic and optomechanical devices employing diamond.

The effect of Fe 3+ doping in Potassium Hydrogen Phthalate single crystals on structural and optical properties

NASA Astrophysics Data System (ADS)

Kumar, R. Ashok; Sivakumar, N.; Vizhi, R. Ezhil; Babu, D. Rajan

2011-02-01

This work investigates the influence of iron doping on Potassium Hydrogen Phthalate (KHP) single crystals by the slow evaporation solution growth technique. Factors such as evaporation rate, solution pH, solute concentration, super saturation limit, etc. are very important in order to have optically transparent single crystals. As part of the work, the effects of metallic salt FeCl 3 in different concentrations were analyzed with pure KHP. Powder X-ray diffraction suggests that the grown crystals are crystallized in the orthorhombic structure. The functional groups and the effect of moisture on the doped crystals can be analyzed with the help of a FTIR spectrum. The pure and doped KHP single crystal shows good transparency in the entire visible region, which is suitable for optical device applications. The refractive indices along b axis of pure and doped KHP single crystals were analyzed by the prism coupling technique. The emission of green light with the use of a Nd:YAG laser ( λ=1064 nm) confirmed the second harmonic generation properties of the grown crystals.

L-Band High Power Amplifiers for CEBAF Linac

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

Fugitt, Jock; Killion, Richard; Nelson, Richard

1990-09-01

The high power portion of the CEBAF RF system utilizes 340 5kW klystrons providing 339 separately controlled outputs. Modulating anodes have been included in the klystron design to provide for economically efficient operation. The design includes shunt regulator-type modulating anode power supplies running from the cathode power supply, and switching filament power supplies. Remotely programmable filament voltage allows maximum cathode life to be realized. Klystron operating setpoint and fast klystron protection logic are provided by individual external CEBAF RF control modules. A single cathode power supply powers a block of eight klystrons. The design includes circulators and custom extrusion andmore » hybrid waveguide components which have allowed reduced physical size and lower cost in the design of the WR-650 waveguide transmission system.« less

Hollow cathode restartable 15 cm diameter ion thruster

NASA Technical Reports Server (NTRS)

Wilbur, P. J.

1973-01-01

The effects of substituting high perveance dished grids for low perveance flat ones on performance variables and plasma properties within a 15 cm modified SERT II thruster are discussed. Results suggest good performance may be achieved as an ion thruster is throttled if the screen grid transparency is decreased with propellant flow rate. Thruster startup tests, which employ a pulsed high voltage tickler electrode between the keeper and the cathode to initiate the discharge, are described. High startup reliability at cathode tip temperatures of about 500 C without excessive component wear over 2000 startup cycles is demonstrated. Testing of a single cusp magnetic field concept of discharge plasma containment is discussed. A theory which explains the observed behavior of the device is presented and proposed thruster modifications and future testing plans are discussed.

Experimental investigation of a 1 kA/cm² sheet beam plasma cathode electron gun.

PubMed

Kumar, Niraj; Pal, Udit Narayan; Pal, Dharmendra Kumar; Prajesh, Rahul; Prakash, Ram

2015-01-01

In this paper, a cold cathode based sheet-beam plasma cathode electron gun is reported with achieved sheet-beam current density ∼1 kA/cm(2) from pseudospark based argon plasma for pulse length of ∼200 ns in a single shot experiment. For the qualitative assessment of the sheet-beam, an arrangement of three isolated metallic-sheets is proposed. The actual shape and size of the sheet-electron-beam are obtained through a non-conventional method by proposing a dielectric charging technique and scanning electron microscope based imaging. As distinct from the earlier developed sheet beam sources, the generated sheet-beam has been propagated more than 190 mm distance in a drift space region maintaining sheet structure without assistance of any external magnetic field.

High performance and durability of order-structured cathode catalyst layer based on TiO2@PANI core-shell nanowire arrays

NASA Astrophysics Data System (ADS)

Chen, Ming; Wang, Meng; Yang, Zhaoyi; Wang, Xindong

2017-06-01

In this paper, an order-structured cathode catalyst layer consisting of Pt-TiO2@PANI core-shell nanowire arrays that in situ grown on commercial gas diffusion layer (GDL) are prepared and applied to membrane electrode assembly (MEA) of proton exchange membrane fuel cell (PEMFC). In order to prepare the TiO2@PANI core-shell nanowire arrays with suitable porosity and prominent conductivity, the morphologies of the TiO2 nanoarray and electrochemical polymerization process of aniline are schematically investigated. The MEA with order-structured cathode catalyst layer is assembled in the single cell to evaluate the electrochemical performance and durability of PEMFC. As a result, the PEMFC with order-structured cathode catalyst layer shows higher peak power density (773.54 mW cm-2) than conventional PEMFC (699.30 mW cm-2). Electrochemically active surface area (ECSA) and charge transfer impedance (Rct) are measured before and after accelerated degradation test (ADT), and the corresponding experimental results indicate the novel cathode structure exhibits a better stability with respect to conventional cathode. The enhanced electrochemical performance and durability toward PEMFC can be ascribed to the order-structured cathode nanoarray structure with high specific surface area increases the utilization of catalyst and reduces the tortuosity of transport pathways, and the synergistic effect between TiO2@PANI support and Pt nanoparticles promotes the high efficiency of electrochemical reaction and improves the stability of catalyst. This research provides a facile and controllable method to prepare order-structured membrane electrode with lower Pt loading for PEMFC in the future.

Novel Low-Cost, Low-Power Miniature Thermionic Cathode Developed for Microwave/Millimeter Wave Tube and Cathode Ray Tube Applications

NASA Technical Reports Server (NTRS)

Wintucky, Edwin G.

1999-01-01

A low cost, small size and mass, low heater power, durable high-performance barium dispenser thermionic cathode has been developed that offers significant advancements in the design, manufacture, and performance of the electron sources used in vacuum electronic devices--such as microwave (and millimeter wave) traveling-wave tubes (TWT's)--and in display devices such as high-brightness, high-resolution cathode ray tubes (CRT's). The lower cathode heater power and the reduced size and mass of the new cathode are expected to be especially beneficial in TWT's for deep space communications, where future missions are requiring smaller spacecraft, higher data transfer rates (higher frequencies and radiofrequency output power), and greater electrical efficiency. Also expected to benefit are TWT's for commercial and government communication satellites, for both low and geosynchronous Earth orbit, with additional benefits offered by lower cost and potentially higher cathode current loading. A particularly important TWT application is in the microwave power module (MPM), which is a hybrid microwave (or millimeter wave) amplifier consisting of a low-noise solid state driver, a vacuum power booster (small TWT), and an electronic power conditioner integrated into a single compact package. The attributes of compactness and potentially high electrical efficiency make the MPM very attractive for many commercial and government (civilian and defense) applications in communication and radar systems. The MPM is already finding application in defense electronic systems and is under development by NASA for deep space communications. However, for the MPM to become competitive and commercially successful, a major reduction in cost must be achieved.

Energy-filtered real- and k-space secondary and energy-loss electron imaging with Dual Emission Electron spectro-Microscope: Cs/Mo(110).

PubMed

Grzelakowski, Krzysztof P

2016-05-01

Since its introduction the importance of complementary k||-space (LEED) and real space (LEEM) information in the investigation of surface science phenomena has been widely demonstrated over the last five decades. In this paper we report the application of a novel kind of electron spectromicroscope Dual Emission Electron spectroMicroscope (DEEM) with two independent electron optical channels for reciprocal and real space quasi-simultaneous imaging in investigation of a Cs covered Mo(110) single crystal by using the 800eV electron beam from an "in-lens" electron gun system developed for the sample illumination. With the DEEM spectromicroscope it is possible to observe dynamic, irreversible processes at surfaces in the energy-filtered real space and in the corresponding energy-filtered kǁ-space quasi-simultaneously in two independent imaging columns. The novel concept of the high energy electron beam sample illumination in the cathode lens based microscopes allows chemically selective imaging and analysis under laboratory conditions. Copyright © 2015 Elsevier B.V. All rights reserved.

Polypropylene oil as fuel for solid oxide fuel cell with samarium doped-ceria (SDC)-carbonate as electrolyte

NASA Astrophysics Data System (ADS)

Syahputra, R. J. E.; Rahmawati, F.; Prameswari, A. P.; Saktian, R.

2017-03-01

The research focusses on converting polypropylene oil as pyrolysis product of polypropylene plastic into an electricity. The converter was a direct liquid fuel-solid oxide fuel cell (SOFC) with cerium oxide based material as electrolyte. The polypropylene vapor flowed into fuel cell, in the anode side and undergo oxidation reaction, meanwhile, the Oxygen in atmosphere reduced into oxygen ion at cathode. The fuel cell test was conducted at 400 - 600 °C. According to GC-MS analysis, the polypropylene oil consist of C8 to C27 hydrocarbon chain. The XRD analysis result shows that Na2CO3 did not change the crystal structure of SDC even increases the electrical conductivity. The maximum power density is 0.079 mW.cm-2 at 773 K. The open circuite voltage is 0.77 volt. Chemical stability test by analysing the single cell at before and after fuel cell test found that ionic migration occured during fuel cell operation. It is supported by the change of elemental composition in the point position of electrolyte and at the electrolyte-electrode interface

Ferrier rearrangement promoted by an electrochemically generated zirconium catalyst.

PubMed

Stevanović, Dragana; Pejović, Anka; Damljanović, Ivan; Minić, Aleksandra; Bogdanović, Goran A; Vukićević, Mirjana; Radulović, Niko S; Vukićević, Rastko D

2015-04-30

In situ generated zirconium catalyst from a sacrificial zirconium anode was successfully applied to promote Ferrier rearrangement of 3,4,5-tri-O-acetyl-D-glucal and 6-deoxy-3,4-di-O-acetyl-L-glucal (3,4-di-O-acetyl-L-rhamnal) in the presence of three thiols and eleven thiophenols as nucleophiles. A simple constant current electrolysis (20 mA, 0.4 F mol(-1)) of an acetonitrile solution of lithium perchlorate (0.1 M) containing the corresponding glycal and S-nucleophiles, using a zirconium anode and a platinum cathode resulted in the successful synthesis of the corresponding 2,3-unsaturated peracetylated thioglycosides (with an average anomer ratio α/β=4.129 in the case of peracetylated D-glucal and 8.740 in the case of L-rhamnal). The same procedure proved to be appropriate in synthesizing dihydropyran derivatives ('C-glycosides') using allyltrimethylsilane as the nucleophile (only 'α-anomers' were obtained). All new compounds were fully characterized by spectral data, whereas single-crystal X-ray analysis was performed for two thioglycosides. Copyright © 2015 Elsevier Ltd. All rights reserved.

Triode for Magnetic Flux Quanta.

PubMed

Vlasko-Vlasov, V K; Colauto, F; Benseman, T; Rosenmann, D; Kwok, W-K

2016-11-15

In an electronic triode, the electron current emanating from the cathode is regulated by the electric potential on a grid between the cathode and the anode. Here we demonstrate a triode for single quantum magnetic field carriers, where the flow of individual magnetic vortices in a superconducting film is regulated by the magnetic potential of striae of soft magnetic strips deposited on the film surface. By rotating an applied in-plane field, the magnetic strip potential can be varied due to changes in the magnetic charges at the strip edges, allowing accelerated or retarded motion of magnetic vortices inside the superconductor. Scaling down our design and reducing the gap width between the magnetic stripes will enable controlled manipulation of individual vortices and creation of single flux quantum circuitry for novel high-speed low-power superconducting electronics.

Electrocatalysis of the Needle-Like NiMoO4 Crystal Toward Urea Oxidation Coupled with H2 Production

NASA Astrophysics Data System (ADS)

Zhou, Mao; Miao, Yuqing

In the International Space Station, urine is considered something to be treated. However, urine is mainly composed of water and urea, while they have been demonstrated as an excellent hydrogen carrier for sustainable energy supply. Through the simple chemical coprecipitation and hydrothermal reaction, the needle-like NiMoO4 crystals were synthesized with the average width around 500nm and length up to 4μm. The resulted products were thoroughly characterized by scanning electron microscopy, energy dispersive X-ray spectrometry, X-ray diffraction, Fourier-transform infrared spectroscopy and ultraviolet-visible spectrum. The needle-like NiMoO4 crystals exhibited excellent electrocatalytic oxidation toward urea at anode in alkali solution, leading to the increased performance of hydrogen evolution reaction at cathode with the lower electrochemical potential and energy consumption required to drive the reaction. The high electrocatalysis of the needle-like NiMoO4 crystals toward urea oxidation reveals their great potential for future application to clean the urine/urea-rich wastewater and to produce hydrogen in space station and environmental wastewater.

Crystal-field analysis of U3+ ions in K2LaX5 (X=Cl, Br or I) single crystals

NASA Astrophysics Data System (ADS)

Karbowiak, M.; Edelstein, N.; Gajek, Z.; Drożdżyński, J.

1998-11-01

An analysis of low temperature absorption spectra of U3+ ions doped in K2LaX5 (X=Cl, Br or I) single crystals is reported. The energy levels of the U3+ ion in the single crystals were assigned and fitted to a semiempirical Hamiltonian representing the combined atomic and crystal-field interactions at the Cs symmetry site. An analysis of the nephelauxetic effect and crystal-field splittings in the series of compounds is also reported.

Averaging of elastic constants for polycrystals

DOE PAGES

Blaschke, Daniel N.

2017-10-13

Many materials of interest are polycrystals, i.e., aggregates of single crystals. Randomly distributed orientations of single crystals lead to macroscopically isotropic properties. Here in this paper, we briefly review strategies of calculating effective isotropic second and third order elastic constants from the single crystal ones. Our main emphasis is on single crystals of cubic symmetry. Specifically, the averaging of third order elastic constants has not been particularly successful in the past, and discrepancies have often been attributed to texturing of polycrystals as well as to uncertainties in the measurement of elastic constants of both poly and single crystals. While thismore » may well be true, we also point out here shortcomings in the theoretical averaging framework.« less

Development of a Single-Crystal Fifth-Generation Nickel Superalloy

NASA Astrophysics Data System (ADS)

Petrushin, N. V.; Elyutin, E. S.; Visik, E. M.; Golynets, S. A.

2017-11-01

The chemical and phase compositions of a rhenium-ruthenium-containing fifth-generation VZhM8 nickel superalloy, which is intended for single-crystal turbine blades of an aviation engine, are calculated using computer simulation. VZhM8 alloy <001>, <011>, and <111> single crystals are fabricated. The microstructure, the γ/γ' misfit, the segregation coefficients of alloying elements, the dissolution temperature of the γ' phase, and the solidus and liquidus temperatures of the VZhM8 alloy single crystals in the as-cast state and after heat treatment are studied. The temperature-time dependences of the static elastic modulus, the short-term mechanical properties, and the long-term strength of the alloy single crystals are determined

Growth and studies of cyclohexylammonium 4-methoxy benzoate single crystal for nonlinear optical applications

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

Sathya, P.; Gopalakrishnan, R., E-mail: krgkrishnan@annauniv.edu

2015-06-24

Cyclohexylammonium 4-Methoxy Benzoate (C4MB) was synthesised and the functional groups were confirmed by FTIR analysis. The purified C4MB (by repeated recrystallisation) was used for single crystal growth. Single crystal of cyclohexylammonium 4-methoxy benzoate was successfully grown by slow evaporation solution growth method at ambient temperature. Structural orientations were determined from single crystal X-ray diffractometer. Optical absorption and cut off wavelength were identified by UV-Visible spectroscopy. Thermal stability of the crystal was studied from thermogravimetric and differential thermal analyses curves. Mechanical stability of the grown crystal was analysed by Vicker’s microhardness tester. The Second Harmonic Generation (SHG) study revealed that themore » C4MB compound exhibits the SHG efficiency 3.3 times greater than KDP crystal.« less

Synthesis, structural, thermal and Hirshfeld surface analysis of novel [1,2,4]triazolo[3,4-b][1,3,4] thiadiazine carrying 1,4-benzothiazine-3-one moiety

NASA Astrophysics Data System (ADS)

Shruthi, C.; Ravindrachary, V.; Guruswamy, B.; Lokanath, N. K.; Kumara, Karthik; Goveas, Janet

2018-05-01

Needle shaped single crystal of the title compound was grown by slow evaporation solution growth technique using ethanol as solvent. The grown single crystal was characterized using FT-IR, Single crystal XRD and Thermal analysis. The FT-IR spectrum confirms the molecular structure and identifies the different functional groups present in the compound. Single crystal XRD study reveals that the crystallized compound belongs to the monoclinic crystal system with P21/c space group and the corresponding cell parameters were identified. The thermal stability of the material was determined using both TGA and DTA analysis. The intermolecular interaction of each individual atom in the crystal lattice was estimated using Hirshfeld surface and finger print analysis.

Influence of solvents on the habit modification of alpha lactose monohydrate single crystals

NASA Astrophysics Data System (ADS)

Parimaladevi, P.; Srinivasan, K.

2013-02-01

Restricted evaporation of solvent method was adopted for the growth of alpha lactose monohydrate single crystals from different solvents. The crystal habits of grown crystals were analysed. The form of crystallization was confirmed by powder x-ray diffraction analysis. Thermal behaviour of the grown crystals was studied by using differential scanning calorimetry.

Analytical studies on the crystal melt interface shape in the Czochralski process for oxide single crystals

NASA Astrophysics Data System (ADS)

Jeong, Ja Hoon; Kang, In Seok

2000-09-01

Effects of the operating conditions on the crystal-melt interface shape are analytically investigated for the Czochralski process of the oxide single crystals. The ideas, which were used for the silicon single-crystal growth by Jeong et al. (J. Crystal Growth 177 (1997) 157), are extended to the oxide single-crystal growth problem by considering the internal radiation in the crystal phase and the melt phase heat transfer with the high Prandtl number. The interface shape is approximated in the simplest form as a quadratic function of radial position and an expression for the deviation from the flat interface shape is derived as a function of operating conditions. The radiative heat transfer rate between the interface and the ambient is computed by calculating the view factors for the curved interface shape with the assumption that the crystal phase is completely transparent. For the melt phase, the well-known results from the thermal boundary layer analysis are applied for the asymptotic case of high Prandtl number based on the idea that the flow field near the crystal-melt interface can be modeled as either a uniaxial or a biaxial flow. Through this work, essential information on the interface shape deformation and the effects of operating conditions are brought out for the oxide single-crystal growth.

Crystal structure, spectral, thermal and dielectric studies of a new zinc benzoate single crystal

NASA Astrophysics Data System (ADS)

Bijini, B. R.; Prasanna, S.; Deepa, M.; Nair, C. M. K.; Rajendra Babu, K.

2012-11-01

Single crystals of zinc benzoate with a novel structure were grown in gel media. Sodium metasilicate of gel density 1.04 g/cc at pH 6 was employed to yield transparent single crystals. The crystal structure of the compound was ascertained by single crystal X-ray diffractometry. It was noted that the crystal belongs to monoclinic system with space group P21/c with unit cell parameters a = 10.669(1) Å, b = 12.995(5) Å, c = 19.119(3) Å, and β = 94.926(3)°. The crystal was seen to possess a linear polymeric structure along b-axis; with no presence of coordinated or lattice water. CHN analysis established the stoichiometric composition of the crystal. The existence of functional groups present in the single crystal system was confirmed by FT-IR studies. The thermal characteristic of the sample was analysed by TGA-DTA techniques, and the sample was found to be thermally stable up to 280 °C. The kinetic and thermodynamic parameters were also determined. UV-Vis spectroscopy corroborated the transparency of the crystal and revealed the optical band gap to be 4 eV. Dielectric studies showed decrease in the dielectric constant of the sample with increase in frequency.

Reliability Studies of Ceramic Capacitors.

DTIC Science & Technology

1983-07-01

increases. This case has been found to be a good approximation for single crystals with high chemical and structural purity. Shallow traps may arise as a...theory, this sudden increase may be otherwise explained. Single crystals of ZnS have been found to exhibit this vertical increase in the current...Smith and Rose observed SCLC behavior in CdS single crystals . Branwood and Tredgold 2 8 and Branwood et al. 2 9 measured BaTiO 3 single crystals and

Reversible conversion of valence-tautomeric copper metal-organic frameworks dependent single-crystal-to-single-crystal oxidation/reduction: a redox-switchable catalyst for C-H bonds activation reaction.

PubMed

Huang, Chao; Wu, Jie; Song, Chuanjun; Ding, Ran; Qiao, Yan; Hou, Hongwei; Chang, Junbiao; Fan, Yaoting

2015-06-28

Upon single-crystal-to-single-crystal (SCSC) oxidation/reduction, reversible structural transformations take place between the anionic porous zeolite-like Cu(I) framework and a topologically equivalent neutral Cu(I)Cu(II) mixed-valent framework. The unique conversion behavior of the Cu(I) framework endowed it as a redox-switchable catalyst for the direct arylation of heterocycle C-H bonds.

Solution-grown organic single-crystalline p-n junctions with ambipolar charge transport.

PubMed

Fan, Congcheng; Zoombelt, Arjan P; Jiang, Hao; Fu, Weifei; Wu, Jiake; Yuan, Wentao; Wang, Yong; Li, Hanying; Chen, Hongzheng; Bao, Zhenan

2013-10-25

Organic single-crystalline p-n junctions are grown from mixed solutions. First, C60 crystals (n-type) form and, subsequently, C8-BTBT crystals (p-type) nucleate heterogeneously on the C60 crystals. Both crystals continue to grow simultaneously into single-crystalline p-n junctions that exhibit ambipolar charge transport characteristics. This work provides a platform to study organic single-crystalline p-n junctions. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Exercise your physics when flying

NASA Astrophysics Data System (ADS)

Baffa, Oswaldo

1999-10-01

Recently, while flying, I found it difficult to sleep and started to pay attention to the television screens in the airplane. There were two types of TV to watch—a large cathode raye tube (CRT)monitor and smaller liquid crystal display (LCD) for passengers sitting near the bulkhead. In one of my glances at the large monitors I noticed that the colors were changing. I looked at the LCD monitors and the colors were fine. What could be happening?

Growth and nonlinear optical characterization of organic single crystal films

NASA Astrophysics Data System (ADS)

Zhou, Ligui

1997-12-01

Organic single crystal films are important for various future applications in photonics and integrated optics. The conventional method for inorganic crystal growth is not suitable for organic materials, and the high temperature melting method is not good for most organic materials due to decomposition problems. We developed a new method-modified shear method-to grow large area organic single crystal thin films which have exceptional nonlinear optical properties and high quality surfaces. Several organic materials (NPP, PNP and DAST) were synthesized and purified before the thin film crystal growth. Organic single crystal thin films were grown from saturated organic solutions using modified shear method. The area of single crystal films were about 1.5 cm2 for PNP, 1 cm2 for NPP and 5 mm2 for DAST. The thickness of the thin films which could be controlled by the applied pressure ranged from 1μm to 10 μm. The single crystal thin films of organic materials were characterized by polarized microscopy, x-ray diffraction, polarized UV-Visible and polarized micro-FTIR spectroscopy. Polarized microscopy showed uniform birefringence and complete extinction with the rotation of the single crystal thin films under crossed- polarization, which indicated high quality single crystals with no scattering. The surface orientation of single crystal thin films was characterized by x-ray diffraction. The molecular orientation within the crystal was further studied by the polarized UV-Visible and Polarized micro-FTIR techniques combined with the x-ray and polarized microscopy results. A Nd:YAG laser with 35 picosecond pulses at 1064nm wavelength was employed to perform the nonlinear optical characterization of the organic single crystal thin films. Two measurement techniques were used to study the crystal films: second harmonic generation (SHG) and electro-optic (EO) effect. SHG results showed that the nonlinear optical coefficient of NPP was 18 times that of LiNbO3, a standard inorganic crystal material, and the nonlinear optical coefficient of PNP was 11 times that of LiNbO3. Electro-optic measurements showed that r11 = 65 pm/V for NPP and r12 = 350 pm/V for DAST. EO modulation effect was also observed using Fabry-Perot interferometry. Waveguide devices are very important for integrated optics. But the fabrication of waveguide devices on the organic single crystal thin films was difficult due to the solubility of the film in common organic solvents. A modified photolithographic technique was employed to make channel waveguides and poly(vinyl alcohol) (PVA) was used as a protective layer in the fabrication of the waveguides. Waveguides with dimensions about 7/mum x 1μm x 1mm were obtained.

Synthesis, growth, structural and optical studies of a novel organic Piperazine (bis) p-toluenesulfonate single crystal.

PubMed

Rekha, P; Peramaiyan, G; NizamMohideen, M; Kumar, R Mohan; Kanagadurai, R

2015-03-15

A novel organic single crystal of Piperazinium (bis) p-toluenesulfonate (PPTS) was grown by a slow evaporation solution growth technique. The structure of the grown crystal was determined using single crystal X-ray diffraction analysis. The PPTS crystal belongs to the triclinic crystal system with space group of P1¯. The presence of functional groups was confirmed by FTIR spectral analysis. The optical transmittance range and cut-off wavelength were identified by UV-vis-NIR spectral studies. The luminescent properties of PPTS crystal were investigated. The thermal behavior of PPTS crystal was studied by TG-DT analyses. Copyright © 2014 Elsevier B.V. All rights reserved.

Structure and Growth Control of Organic-Inorganic Halide Perovskites for Optoelectronics: From Polycrystalline Films to Single Crystals.

PubMed

Chen, Yani; He, Minhong; Peng, Jiajun; Sun, Yong; Liang, Ziqi

2016-04-01

Recently, organic-inorganic halide perovskites have sparked tremendous research interest because of their ground-breaking photovoltaic performance. The crystallization process and crystal shape of perovskites have striking impacts on their optoelectronic properties. Polycrystalline films and single crystals are two main forms of perovskites. Currently, perovskite thin films have been under intensive investigation while studies of perovskite single crystals are just in their infancy. This review article is concentrated upon the control of perovskite structures and growth, which are intimately correlated for improvements of not only solar cells but also light-emitting diodes, lasers, and photodetectors. We begin with the survey of the film formation process of perovskites including deposition methods and morphological optimization avenues. Strategies such as the use of additives, thermal annealing, solvent annealing, atmospheric control, and solvent engineering have been successfully employed to yield high-quality perovskite films. Next, we turn to summarize the shape evolution of perovskites single crystals from three-dimensional large sized single crystals, two-dimensional nanoplates, one-dimensional nanowires, to zero-dimensional quantum dots. Siginificant functions of perovskites single crystals are highlighted, which benefit fundamental studies of intrinsic photophysics. Then, the growth mechanisms of the previously mentioned perovskite crystals are unveiled. Lastly, perspectives for structure and growth control of perovskites are outlined towards high-performance (opto)electronic devices.

Ames Lab 101: Single Crystal Growth

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

Schlagel, Deborah

2013-09-27

Ames Laboratory scientist Deborah Schlagel talks about the Lab's research in growing single crystals of various metals and alloys. The single crystal samples are vital to researchers' understanding of the characteristics of a materials and what gives these materials their particular properties.

Ames Lab 101: Single Crystal Growth

ScienceCinema

Schlagel, Deborah

2018-01-16

Ames Laboratory scientist Deborah Schlagel talks about the Lab's research in growing single crystals of various metals and alloys. The single crystal samples are vital to researchers' understanding of the characteristics of a materials and what gives these materials their particular properties.

Elastic response of zone axis (001)-oriented PWA 1480 single crystal: The influence of secondary orientation

NASA Technical Reports Server (NTRS)

Kalluri, Sreeramesh; Abdul-Aziz, Ali; Mcgaw, Michael A.

1991-01-01

The influence of secondary orientation on the elastic response of a zone axis (001)-oriented nickel-base single-crystal superalloy, PWA 1480, was investigated under mechanical loading conditions by applying finite element techniques. Elastic stress analyses were performed with a commercially available finite element code. Secondary orientation of the single-crystal superalloy was offset with respect to the global coordinate system in increments from 0 to 90 deg and stresses developed within the single crystal were determined for each loading condition. The results indicated that the stresses were strongly influenced by the angular offset between the secondary crystal orientation and the global coordinate system. The degree of influence was found to vary with the type of loading condition (mechanical, thermal, or combined) imposed on the single-crystal superalloy.

Sustainable Hypersaline Microbial Fuel Cells: Inexpensive Recyclable Polymer Supports for Carbon Nanotube Conductive Paint Anodes.

PubMed

Grattieri, Matteo; Shivel, Nelson D; Sifat, Iram; Bestetti, Massimiliano; Minteer, Shelley D

2017-05-09

Microbial fuel cells are an emerging technology for wastewater treatment, but to be commercially viable and sustainable, the electrode materials must be inexpensive, recyclable, and reliable. In this study, recyclable polymeric supports were explored for the development of anode electrodes to be applied in single-chamber microbial fuel cells operated in field under hypersaline conditions. The support was covered with a carbon nanotube (CNT) based conductive paint, and biofilms were able to colonize the electrodes. The single-chamber microbial fuel cells with Pt-free cathodes delivered a reproducible power output after 15 days of operation to achieve 12±1 mW m -2 at a current density of 69±7 mA m -2 . The decrease of the performance in long-term experiments was mostly related to inorganic precipitates on the cathode electrode and did not affect the performance of the anode, as shown by experiments in which the cathode was replaced and the fuel cell performance was regenerated. The results of these studies show the feasibility of polymeric supports coated with CNT-based paint for microbial fuel cell applications. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

High performance cobalt-free Cu1.4Mn1.6O4 spinel oxide as an intermediate temperature solid oxide fuel cell cathode

NASA Astrophysics Data System (ADS)

Zhen, Shuying; Sun, Wang; Li, Peiqian; Tang, Guangze; Rooney, David; Sun, Kening; Ma, Xinxin

2016-05-01

In this work Cu1.4Mn1.6O4 (CMO) spinel oxide is prepared and evaluated as a novel cobalt-free cathode for intermediate temperature solid oxide fuel cells (IT-SOFCs). Single phase CMO powder with cubic structure is identified using XRD. XPS results confirm that mixed Cu+/Cu2+ and Mn3+/Mn4+ couples exist in the CMO sample, and a maximum conductivity of 78 S cm-1 is achieved at 800 °C. Meanwhile, CMO oxide shows good thermal and chemical compatibility with a 10 mol% Sc2O3 stabilized ZrO2 (ScSZ) electrolyte material. Impedance spectroscopy measurements reveals that CMO exhibits a low polarization resistance of 0.143 Ω cm2 at 800 °C. Furthermore, a Ni-ScSZ/ScSZ/CMO single cell demonstrates a maximum power density of 1076 mW cm-2 at 800 °C under H2 (3% H2O) as the fuel and ambient air as the oxidant. These results indicate that Cu1.4Mn1.6O4 is a superior and promising cathode material for IT-SOFCs.

Rapid preparation of high electrochemical performance LiFePO4/C composite cathode material with an ultrasonic-intensified micro-impinging jetting reactor.

PubMed

Dong, Bin; Huang, Xiani; Yang, Xiaogang; Li, Guang; Xia, Lan; Chen, George

2017-11-01

A joint chemical reactor system referred to as an ultrasonic-intensified micro-impinging jetting reactor (UIJR), which possesses the feature of fast micro-mixing, was proposed and has been employed for rapid preparation of FePO 4 particles that are amalgamated by nanoscale primary crystals. As one of the important precursors for the fabrication of lithium iron phosphate cathode, the properties of FePO 4 nano particles significantly affect the performance of the lithium iron phosphate cathode. Thus, the effects of joint use of impinging stream and ultrasonic irradiation on the formation of mesoporous structure of FePO 4 nano precursor particles and the electrochemical properties of amalgamated LiFePO 4 /C have been investigated. Additionally, the effects of the reactant concentration (C=0.5, 1.0 and 1.5molL -1 ), and volumetric flow rate (V=17.15, 51.44, and 85.74mLmin -1 ) on synthesis of FePO 4 ·2H 2 O nucleus have been studied when the impinging jetting reactor (IJR) and UIJR are to operate in nonsubmerged mode. It was affirmed from the experiments that the FePO 4 nano precursor particles prepared using UIJR have well-formed mesoporous structures with the primary crystal size of 44.6nm, an average pore size of 15.2nm, and a specific surface area of 134.54m 2 g -1 when the reactant concentration and volumetric flow rate are 1.0molL -1 and 85.74mLmin -1 respectively. The amalgamated LiFePO 4 /C composites can deliver good electrochemical performance with discharge capacities of 156.7mAhg -1 at 0.1C, and exhibit 138.0mAhg -1 after 100 cycles at 0.5C, which is 95.3% of the initial discharge capacity. Copyright © 2017. Published by Elsevier B.V.

Remarkable lowering in the synthesis temperature of LiMn2O4via citrate solution-gel synthesis facilitated by ethanol.

PubMed

Maino, G; Carleer, R; Marchal, W; Bonneux, G; Hardy, A; Van Bael, M K

2017-11-07

LiMn 2 O 4 (LMO) is interesting from the viewpoint of its energy storage applications as it is a cathode in lithium ion batteries (LIB), which contains no rare, toxic or expansive elements, while it provides a high theoretical capacity (148 mA h g -1 ) at a reasonable voltage (4 V region) and a higher thermal stability compared to cobalt based cathodes and has a good rechargeability and cycling stability due to its spinel structure. Low temperature synthesis routes for cathode materials are currently gaining attention, in order to decrease the ecological footprint of the final LIB. Here, the crystallization temperature of LMO by a citrate based solution-gel synthesis was significantly lowered, to as low as 250 °C by the addition of ethanol to the precursor. The role of ethanol in this synthesis process was explored. It was found to lead to a considerable increase in the oxidation rate of the redox couple Mn 2+ /Mn 3+ , a lowering of the precursor decomposition temperature by 200 °C, besides a drastic decrease in the crystallization temperature (reaching 250 °C). Moreover, the main cause was identified to be an esterification reaction of ethanol with the carboxylic acid in the precursor complexes, taking place before the oxide formation. The insights obtained strengthen the knowledge regarding citrato-Mn 2+ /Mn 3+ complexes present in aqueous solution-gel synthesis routes and are relevant for the preparation of various manganese containing oxides. Moreover, the precursor developed opens up a new possibility for the low temperature synthesis of LMO powders and thin films for application in LIB. In the case of thin film batteries, the low temperature processing provides compatibility with other materials in the thin film battery stack, avoiding undesired oxidations or interfacial reactions.

Single Crystal Membranes

NASA Technical Reports Server (NTRS)

Stormont, R. W.; Morrison, A.

1974-01-01

Single crystal a- and c-axis tubes and ribbons of sodium beta-alumina and sodium magnesium beta-alumina were grown from sodium oxide rich melts. Additional experiments grew ribbon crystals containing sodium magnesium beta, beta double prime, beta triple prime, and beta quadruple prime. A high pressure crystal growth chamber, sodium oxide rich melts, and iridium for all surfaces in contact with the melt were combined with the edge-defined, film-fed growth technique to grow the single crystal beta-alumina tubes and ribbons. The crystals were characterized using metallographic and X-ray diffraction techniques, and wet chemical analysis was used to determine the sodium, magnesium, and aluminum content of the grown crystals.

Study on structural, morphological, optical and thermal properties of guanidine carbonate doped nickel sulfate hexahydrate crystal.

PubMed

Silambarasan, A; Rajesh, P; Ramasamy, P

2015-01-05

The single crystal of guanidine carbonate doped nickel sulfate hexahydrate was grown from solution for ultraviolet filters. The single crystal XRD confirms that the grown single crystal belongs to the tetragonal system with the space group of P4₁2₁2. The crystallinity of the grown crystal was estimated by powder X-ray diffraction studies. The optical transmission and thermal stability of as-grown guanidine carbonate doped nickel sulfate single crystals have been studied. The optical transmission spectrum demonstrates the characteristics of ultraviolet filters. The TG/DTA studies confirm the thermal properties of grown crystals. Thermo-gravimetric analysis showed that the dehydration temperature of the guanidine carbonate doped nickel sulfate crystal is about 100 °C, which is much higher than that of pure nickel sulfate hexahydrate (NSH) crystals which is 72 °C. The growth behaviors and dislocation density were detected under the high resolution XRD and etching studies respectively. Copyright © 2014 Elsevier B.V. All rights reserved.

Room temperature aluminum antimonide radiation detector and methods thereof

DOEpatents

Lordi, Vincenzo; Wu, Kuang Jen J.; Aberg, Daniel; Erhart, Paul; Coombs, III, Arthur W; Sturm, Benjamin W

2015-03-03

In one embodiment, a method for producing a high-purity single crystal of aluminum antimonide (AlSb) includes providing a growing environment with which to grow a crystal, growing a single crystal of AlSb in the growing environment which comprises hydrogen (H.sub.2) gas to reduce oxide formation and subsequent incorporation of oxygen impurities in the crystal, and adding a controlled amount of at least one impurity to the growing environment to effectively incorporate at least one dopant into the crystal. In another embodiment, a high energy radiation detector includes a single high-purity crystal of AlSb, a supporting structure for the crystal, and logic for interpreting signals obtained from the crystal which is operable as a radiation detector at a temperature of about 25.degree. C. In one embodiment, a high-purity single crystal of AlSb includes AlSb and at least one dopant selected from a group consisting of selenium (Se), tellurium (Te), and tin (Sn).

Low Leakage Superconducting Tunnel Junctions with a Single Crystal Al2O3 Barrier

DTIC Science & Technology

2016-03-30

have recently implemented Josephson junction superconducting devices into qubits [1-6]. Before a multi -qubit quantum computer is realized, however...Low-Leakage Superconducting Tunnel Junctions with a Single-Crystal Al2O3 Barrier* S Oh1,2, K Cicak1, R McDermott3, K B Cooper3, K D Osborn1, R W...growth scheme for single-crystal Al2O3 tunnel barriers. The barriers are epitaxially grown on single-crystal rhenium (Re) base electrodes that are

Operation of a gated field emitter using an individual carbon nanofiber cathode

NASA Astrophysics Data System (ADS)

Guillorn, M. A.; Melechko, A. V.; Merkulov, V. I.; Ellis, E. D.; Britton, C. L.; Simpson, M. L.; Lowndes, D. H.; Baylor, L. R.

2001-11-01

We report on the operation of an integrated gated cathode device using a single vertically aligned carbon nanofiber as the field emission element. This device is capable of operation in a moderate vacuum for extended periods of time without experiencing a degradation of performance. Less than 1% of the total emitted current is collected by the gate electrode, indicating that the emitted electron beam is highly collimated. As a consequence, this device is ideal for applications that require well-focused electron emission from a microscale structure.

Electrolyte chemistry control in electrodialysis processing

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

Hayes, Thomas D.; Severin, Blaine F.

Methods for controlling electrolyte chemistry in electrodialysis units having an anode and a cathode each in an electrolyte of a selected concentration and a membrane stack disposed therebetween. The membrane stack includes pairs of cationic selective and anionic membranes to segregate increasingly dilute salts streams from concentrated salts stream. Electrolyte chemistry control is via use of at least one of following techniques: a single calcium exclusionary cationic selective membrane at a cathode cell boundary, an exclusionary membrane configured as a hydraulically isolated scavenger cell, a multivalent scavenger co-electrolyte and combinations thereof.

Method of manufacturing carbon nanotubes

NASA Technical Reports Server (NTRS)

Benavides, Jeanette M. (Inventor); Leidecker, Henning W. (Inventor); Frazier, Jeffrey (Inventor)

2004-01-01

A process for manufacturing carbon nanotubes, including a step of inducing electrical current through a carbon anode and a carbon cathode under conditions effective to produce the carbon nanotubes, wherein the carbon cathode is larger than the carbon anode. Preferably, a welder is used to induce the electrical current via an arc welding process. Preferably, an exhaust hood is placed on the anode, and the process does not require a closed or pressurized chamber. The process provides high-quality, single-walled carbon nanotubes, while eliminating the need for a metal catalyst.

Hydrogen induced fracture characteristics of single crystal nickel-based superalloys

NASA Technical Reports Server (NTRS)

Chen, Po-Shou; Wilcox, Roy C.

1990-01-01

A stereoscopic method for use with x ray energy dispersive spectroscopy of rough surfaces was adapted and applied to the fracture surfaces single crystals of PWA 1480E to permit rapid orientation determinations of small cleavage planes. The method uses a mathematical treatment of stereo pair photomicrographs to measure the angle between the electron beam and the surface normal. One reference crystal orientation corresponding to the electron beam direction (crystal growth direction) is required to perform this trace analysis. The microstructure of PWA 1480E was characterized before fracture analysis was performed. The fracture behavior of single crystals of the PWA 1480E nickel-based superalloy was studied. The hydrogen-induced fracture behavior of single crystals of the PWA 1480E nickel-based superalloy was also studied. In order to understand the temperature dependence of hydrogen-induced embrittlement, notched single crystals with three different crystal growth orientations near zone axes (100), (110), and (111) were tensile tested at 871 C (1600 F) in both helium and hydrogen atmospheres at 34 MPa. Results and conclusions are given.

Attenuation of thermal neutrons by an imperfect single crystal

NASA Astrophysics Data System (ADS)

Naguib, K.; Adib, M.

1996-06-01

A semi-empirical formula is given which allows one to calculate the total thermal cross section of an imperfect single crystal as a function of crystal constants, temperature and neutron energy E, in the energy range between 3 meV and 10 eV. The formula also includes the contribution of the parasitic Bragg scattering to the total cross section that takes into account the crystal mosaic spread value and its orientation with respect to the neutron beam direction. A computer program (ISCANF) was developed to calculate the total attenuation of neutrons using the proposed formula. The ISCANF program was applied to investigate the neutron attenuation through a copper single crystal. The calculated values of the neutron transmission through the imperfect copper single crystal were fitted to the measured ones in the energy range 3 - 40 meV at different crystal orientations. The result of fitting shows that use of the computer program ISCANF allows one to predict the behaviour of the total cross section of an imperfect copper single crystal for the whole energy range.

Seeded growth of boron arsenide single crystals with high thermal conductivity

NASA Astrophysics Data System (ADS)

Tian, Fei; Song, Bai; Lv, Bing; Sun, Jingying; Huyan, Shuyuan; Wu, Qi; Mao, Jun; Ni, Yizhou; Ding, Zhiwei; Huberman, Samuel; Liu, Te-Huan; Chen, Gang; Chen, Shuo; Chu, Ching-Wu; Ren, Zhifeng

2018-01-01

Materials with high thermal conductivities are crucial to effectively cooling high-power-density electronic and optoelectronic devices. Recently, zinc-blende boron arsenide (BAs) has been predicted to have a very high thermal conductivity of over 2000 W m-1 K-1 at room temperature by first-principles calculations, rendering it a close competitor for diamond which holds the highest thermal conductivity among bulk materials. Experimental demonstration, however, has proved extremely challenging, especially in the preparation of large high quality single crystals. Although BAs crystals have been previously grown by chemical vapor transport (CVT), the growth process relies on spontaneous nucleation and results in small crystals with multiple grains and various defects. Here, we report a controllable CVT synthesis of large single BAs crystals (400-600 μm) by using carefully selected tiny BAs single crystals as seeds. We have obtained BAs single crystals with a thermal conductivity of 351 ± 21 W m-1 K-1 at room temperature, which is almost twice as conductive as previously reported BAs crystals. Further improvement along this direction is very likely.

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

Ji, Xiaoyu; Lei, Shiming; Yu, Shih -Ying

Semiconductor core optical fibers with a silica cladding are of great interest in nonlinear photonics and optoelectronics applications. Laser crystallization has been recently demonstrated for crystallizing amorphous silicon fibers into crystalline form. Here we explore the underlying mechanism by which long single-crystal silicon fibers, which are novel platforms for silicon photonics, can be achieved by this process. Using finite element modeling, we construct a laser processing diagram that reveals a parameter space within which single crystals can be grown. Utilizing this diagram, we illustrate the creation of single-crystal silicon core fibers by laser crystallizing amorphous silicon deposited inside silica capillarymore » fibers by high-pressure chemical vapor deposition. The single-crystal fibers, up to 5.1 mm long, have a very welldefined core/cladding interface and a chemically pure silicon core that leads to very low optical losses down to ~0.47-1dB/cm at the standard telecommunication wavelength (1550 nm). Furthermore, tt also exhibits a photosensitivity that is comparable to bulk silicon. Creating such laser processing diagrams can provide a general framework for developing single-crystal fibers in other materials of technological importance.« less

Mid-IR supercontinuum generation and applications: a review

NASA Astrophysics Data System (ADS)

Yin, Shizhuo; Ruffin, Paul; Brantley, Christina; Edwards, Eugene; Luo, Claire

2014-09-01

In this paper, a review on mid-IR supercontinuum generation (SCG) and its applications is presented. First, the physical mechanism of the supercontinuum generation in IR crystal fiber is introduced. Second, the recent progress on IR single crystal fiber, in particular ultrathin core double cladding IR single crystal fiber is described. Third, the transmission characteristics of mid-IR crystal fiber is illustrated. Fourth, the mid-IR supercontinuum generation in IR single crystal fiber is presented. Finally, the application of IR supercontinuum for smart target recognition is illustrated

Size dependence of nanoscale wear of silicon carbide

Treesearch

Chaiyapat Tangpatjaroen; David Grierson; Steve Shannon; Joseph E. Jakes; Izabela Szlufarska

2017-01-01

Nanoscale, single-asperity wear of single-crystal silicon carbide (sc- SiC) and nanocrystalline silicon carbide (nc-SiC) is investigated using single-crystal diamond nanoindenter tips and nanocrystalline diamond atomic force microscopy (AFM) tips under dry conditions, and the wear behavior is compared to that of single-crystal silicon with both thin and thick native...

Anisotropic Laminar Piezocomposite Actuator Incorporating Machined PMN-PT Single Crystal Fibers

NASA Technical Reports Server (NTRS)

Wilkie, W. Keats; Inman, Daniel J.; Lloyd, Justin M.; High, James W.

2006-01-01

The design, fabrication, and testing of a flexible, laminar, anisotropic piezoelectric composite actuator utilizing machined PMN-32%PT single crystal fibers is presented. The device consists of a layer of rectangular single crystal piezoelectric fibers in an epoxy matrix, packaged between interdigitated electrode polyimide films. Quasistatic free-strain measurements of the single crystal device are compared with measurements from geometrically identical specimens incorporating polycrystalline PZT-5A and PZT-5H piezoceramic fibers. Free-strain actuation of the single crystal actuator at low bipolar electric fields (+/- 250 V/mm) is approximately 400% greater than that of the baseline PZT-5A piezoceramic device, and 200% greater than that of the PZT-5H device. Free-strain actuation under high unipolar electric fields (0-4kV/mm) is approximately 200% of the PZT-5A baseline device, and 150% of the PZT-5H alternate piezoceramic device. Performance increases at low field are qualitatively consistent with predicted increases based on scaling the low-field d33 piezoelectric constants of the respective piezoelectric materials. High-field increases are much less than scaled d33 estimates, but appear consistent with high-field freestrain measurements reported for similar bulk single-crystal and piezoceramic compositions. Measurements of single crystal actuator capacitance and coupling coefficient are also provided. These properties were poorly predicted using scaled bulk material dielectric and coupling coefficient data. Rules-of-mixtures calculations of the effective elastic properties of the single crystal device and estimated actuation work energy densities are also presented. Results indicate longitudinal stiffnesses significantly lower (50% less) than either piezoceramic device. This suggests that single-crystal piezocomposite actuators will be best suited to low induced-stress, high strain and deflection applications.

Anisotropic Piezocomposite Actuator Incorporating Machined PMN-PT Single Crystal Fibers

NASA Technical Reports Server (NTRS)

Wilkie, W. Keats; Inman, Daniel J.; Lloyd, Justin M.; High, James W.

2004-01-01

The design, fabrication, and testing of a flexible, planar, anisotropic piezoelectric composite actuator utilizing machined PMN-32%PT single crystal fibers is presented. The device consists of a layer of rectangular single crystal piezoelectric fibers in an epoxy matrix, packaged between interdigitated electrode polyimide films. Quasistatic free-strain measurements of the single crystal device are compared with measurements from geometrically identical specimens incorporating polycrystalline PZT-5A and PZT-5H piezoceramic fibers. Free-strain actuation of the single crystal actuator at low bipolar electric fields (+/- 250 V/mm) is approximately 400% greater than that of the baseline PZT-5A piezoceramic device, and 200% greater than that of the PZT-5H device. Free-strain actuation under high unipolar electric fields (0-4kV/mm) is approximately 200% of the PZT-5A baseline device, and 150% of the PZT-5H alternate piezoceramic device. Performance increases at low field are qualitatively consistent with predicted increases based on scaling the low-field d(sub 33) piezoelectric constants of the respective piezoelectric materials. High-field increases are much less than scaled d(sub 33) estimates, but appear consistent with high-field freestrain measurements reported for similar bulk single-crystal and piezoceramic compositions. Measurements of single crystal actuator capacitance and coupling coefficient are also provided. These properties were poorly predicted using scaled bulk material dielectric and coupling coefficient data. Rules-of-mixtures calculations of the effective elastic properties of the single crystal device and estimated actuation work energy densities are also presented. Results indicate longitudinal stiffnesses significantly lower (50% less) than either piezoceramic device. This suggests that single-crystal piezocomposite actuators will be best suited to low induced-stress, high strain and deflection applications.

Three-Dimensional Conformation of Folded Polymers in Single Crystals

NASA Astrophysics Data System (ADS)

Hong, You-lee; Yuan, Shichen; Li, Zhen; Ke, Yutian; Nozaki, Koji; Miyoshi, Toshikazu

2015-10-01

The chain-folding mechanism and structure of semicrystalline polymers have long been controversial. Solid-state NMR was applied to determine the chain trajectory of 13C CH3 -labeled isotactic poly(1-butene) (i PB 1 ) in form III chiral single crystals blended with nonlabeled i PB 1 crystallized in dilute solutions under low supercooling. An advanced 13C - 13C double-quantum NMR technique probing the spatial proximity pattern of labeled 13C nuclei revealed that the chains adopt a three-dimensional (3D) conformation in single crystals. The determined results indicate a two-step crystallization process of (i) cluster formation via self-folding in the precrystallization stage and (ii) deposition of the nanoclusters as a building block at the growth front in single crystals.

High-pressure floating-zone growth of perovskite nickelate LaNiO 3 single crystals

DOE PAGES

Zhang, Junjie; Zheng, Hong; Ren, Yang; ...

2017-04-07

We report the first single crystal growth of the correlated metal LaNiO 3 using a high-pressure optical-image floating zone furnace. The crystals were studied using single crystal/powder X-ray diffraction, resistivity, specific heat, and magnetic susceptibility. The availability of bulk LaNiO 3 crystals will (i) promote deep understanding in this correlated material, including the mechanism of enhanced paramagnetic susceptibility, and (ii) provide rich opportunities as a substrate for thin film growth such as important ferroelectric and/or multiferroic materials. As a result, this study demonstrates the power of high pO 2 single crystal growth of nickelate perovskites and correlated electron oxides moremore » generally.« less

Solution-processed, Self-organized Organic Single Crystal Arrays with Controlled Crystal Orientation

PubMed Central

Kumatani, Akichika; Liu, Chuan; Li, Yun; Darmawan, Peter; Takimiya, Kazuo; Minari, Takeo; Tsukagoshi, Kazuhito

2012-01-01

A facile solution process for the fabrication of organic single crystal semiconductor devices which meets the demand for low-cost and large-area fabrication of high performance electronic devices is demonstrated. In this paper, we develop a bottom-up method which enables direct formation of organic semiconductor single crystals at selected locations with desired orientations. Here oriented growth of one-dimensional organic crystals is achieved by using self-assembly of organic molecules as the driving force to align these crystals in patterned regions. Based upon the self-organized organic single crystals, we fabricate organic field effect transistor arrays which exhibit an average field-effect mobility of 1.1 cm2V−1s−1. This method can be carried out under ambient atmosphere at room temperature, thus particularly promising for production of future plastic electronics. PMID:22563523

Effect of Crystal Orientation on Analysis of Single-Crystal, Nickel-Based Turbine Blade Superalloys

NASA Technical Reports Server (NTRS)

Swanson, G. R.; Arakere, N. K.

2000-01-01

High-cycle fatigue-induced failures in turbine and turbopump blades is a pervasive problem. Single-crystal nickel turbine blades are used because of their superior creep, stress rupture, melt resistance, and thermomechanical fatigue capabilities. Single-crystal materials have highly orthotropic properties making the position of the crystal lattice relative to the part geometry a significant and complicating factor. A fatigue failure criterion based on the maximum shear stress amplitude on the 24 octahedral and 6 cube slip systems is presented for single-crystal nickel superalloys (FCC crystal). This criterion greatly reduces the scatter in uniaxial fatigue data for PWA 1493 at 1,200 F in air. Additionally, single-crystal turbine blades used in the Space Shuttle main engine high pressure fuel turbopump/alternate turbopump are modeled using a three-dimensional finite element (FE) model. This model accounts for material orthotrophy and crystal orientation. Fatigue life of the blade tip is computed using FE stress results and the failure criterion that was developed. Stress analysis results in the blade attachment region are also presented. Results demonstrate that control of crystallographic orientation has the potential to significantly increase a component's resistance to fatigue crack growth without adding additional weight or cost.