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We report improvements in weld technology in support of our efforts to produce a commercial, long-life, miniature reservoir cathode. We have found that the laser weld between sintered tungsten pellet and reservoir sleeve can be ma...
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We report improvements in weld technology in support of our efforts to produce a commercial, long-life, miniature reservoir cathode. We have found that the laser weld between sintered tungsten pellet and reservoir sleeve can be made reliably hermetic if we apply a subsequent coating of molybdenum-ruthenium brazing alloy to the sides of the pellet and especially to the weld region. The emissive material is then inserted in the open end of the reservoir sleeve, which is then closed by a secondary weld. This secondary weld is reliably hermetic without the Mo-Ru coating, because it does not involve the porous tungsten matrix. Moreover, we have discovered an inspection procedure that allows us to check weld hermeticity at each assembly step. Thermal cycling tests indicate good weld integrity. Emission life testing is proceeding. (c) 2005 Elsevier B.V. All rights reserved..
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In order to improve the activation characteristics and emission ability of the conventional Ir-coated impregnated tungsten cathodes, a new type of dispenser cathode with ternary alloy Ir/Re/W coating was developed. The improved ca...
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In order to improve the activation characteristics and emission ability of the conventional Ir-coated impregnated tungsten cathodes, a new type of dispenser cathode with ternary alloy Ir/Re/W coating was developed. The improved cathodes show higher emission current density and faster activation characteristics than that of the conventional pure Ir-coated impregnated tungsten cathodes. X-ray photoelectron spectroscopy (XPS) was used to analyze the element compositions on the surface of the cathodes coated with pure It and IdRe/W alloy. The results show that for pure It coating cathode, binary alloy (Ir/W) is formed. The surface atom concentration is near 50150 after full activation. For ternary alloy coating cathode, the surface atom concentration has changed from 35%Ir-25%Re-40%W to 33%Ir-19%Re-48%W before and after activation. (c) 2005 Elsevier B.V. All rights reserved.
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The electrolysis of CO_2 is examined in a proton conducting solid electrolyser using BaCe_(0.5)Zr_(0.3)Y_(0.16)Zn _(0.04)O_(3 - δ) as the electrolyte, nickel as the anode to oxidize H_2O/H_2 and copper, nickel or iron as the cath...
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The electrolysis of CO_2 is examined in a proton conducting solid electrolyser using BaCe_(0.5)Zr_(0.3)Y_(0.16)Zn _(0.04)O_(3 - δ) as the electrolyte, nickel as the anode to oxidize H_2O/H_2 and copper, nickel or iron as the cathode to reduce CO_2. The electrolyte and porous scaffolds were prepared by tape casting and the electrodes by impregnation. During electrolysis at 600 C, currents as high as 35 mA/cm_2 (iron), 20 mA/cm_2 (copper) or 15 mA/cm_2 (nickel) at 1.5 V pass through the 200 μm thick electrolytes. Small additions of Pt improve considerably the performance of the electrodes. For iron based cathodes Faradaic efficiencies up to 100% are achieved with production rates of H_2 ≈ 0.14 μmol/cm~2 s, H_2O ≈ 0.25 μmol/cm~2 s and CO ≈ 0.05 μmol/cm~2 s. The possibilities of increasing these yields are discussed.
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摘要 :
The electrolysis of CO_2 is examined in a proton conducting solid electrolyser using BaCe_(0.5)Zr_(0.3)Y_(0.16)Zn _(0.04)O_(3 - δ) as the electrolyte, nickel as the anode to oxidize H_2O/H_2 and copper, nickel or iron as the cath...
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The electrolysis of CO_2 is examined in a proton conducting solid electrolyser using BaCe_(0.5)Zr_(0.3)Y_(0.16)Zn _(0.04)O_(3 - δ) as the electrolyte, nickel as the anode to oxidize H_2O/H_2 and copper, nickel or iron as the cathode to reduce CO_2. The electrolyte and porous scaffolds were prepared by tape casting and the electrodes by impregnation. During electrolysis at 600 C, currents as high as 35 mA/cm_2 (iron), 20 mA/cm_2 (copper) or 15 mA/cm_2 (nickel) at 1.5 V pass through the 200 μm thick electrolytes. Small additions of Pt improve considerably the performance of the electrodes. For iron based cathodes Faradaic efficiencies up to 100% are achieved with production rates of H_2 ≈ 0.14 μmol/cm~2 s, H_2O ≈ 0.25 μmol/cm~2 s and CO ≈ 0.05 μmol/cm~2 s. The possibilities of increasing these yields are discussed.
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In December 2005 the Hamburg aluminum smelter was shut
down. At the end of 2006, TRIMET ALUMINUM AG was able
to purchase the assets and successfully restarted the potlines in
2007. In December 2007 the plant was operating at fu...
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In December 2005 the Hamburg aluminum smelter was shut
down. At the end of 2006, TRIMET ALUMINUM AG was able
to purchase the assets and successfully restarted the potlines in
2007. In December 2007 the plant was operating at full capacity
again, after facing serious supply limitation of pot lining materials
throughout the year. To be able to reach full production at record
time, unproven Eastern European and Chinese cathodes had to be
acquired. Until August 2008 45 pots with Eastern European
cathodes and 46 pots with Chinese cathodes were started. In
addition to these, 149 old linings that had been idle for more than
one year were restarted. This paper highlights operational
experience with these different groups of pots and describes the
success story of the first year of operation after the restart without
losing a single pot.
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In an impressed current cathodic protection system (ICCP) to protect structures against corrosion, the efficient operation depends on the proper selection of the electrodes, particularly the anode, chosen considering the structure...
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In an impressed current cathodic protection system (ICCP) to protect structures against corrosion, the efficient operation depends on the proper selection of the electrodes, particularly the anode, chosen considering the structure to be protected and the environment in which it is located. The nature and overpotential of the anodic reaction determine the operation costs of an ICCP system so that proper anode selection is critically important for an ICCP system to function efficiently. Commercial anodes based on titanium substrates coated with iridium–tantalum oxide mixtures (IrO2-Ta2O5/Ti) are frequently used for this purpose due to low operating overpotentials. However, the gradual passivation of its surface limits its useful life and increases its operating costs, so it is necessary to seek competitive alternatives for its replacement. This study aimed to determine the feasibility of using carbon steel substrates coated with nickel/cobalt/boron (NiCoB/CS) as a viable low-cost alternative to replace IrO2-Ta2O5/Ti anodes in ICCP systems. Comparison between the electrochemical behavior and the corrosion resistance of both types of electrodes shows that the NiCoB/CS anode shows a good electrocatalytic activity and a higher corrosion resistance than IrO2-Ta2O5/Ti coated anodes, indicating that the NiCoB/CS anodes are promising low-cost candidates for ICCP systems.
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Nowadays, the cathodic protection is a common way of additional corrosion protection of buried structures. This protection is usually accompanied by cathodic polarisation on the protective potential of -850 mV(CSE). Its function i...
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Nowadays, the cathodic protection is a common way of additional corrosion protection of buried structures. This protection is usually accompanied by cathodic polarisation on the protective potential of -850 mV(CSE). Its function is to prevent undesirable corrosion rates, in case the coating protection fails. Objective was to predict a state in terms of passivity or activity in which a carbon steel is in. And to do so, there is a monitoring of pH values by amphoteric metals, which would track pH changes of cathodically protected material in a soil. For pH detection, Al and Zn, were used. Main aim was to track corrosion rate of these amphoteric metals as a most reliable way to predict pH changes. Cathodic protection led to higher pH values of model soil located closely to surface of protected material. In case of carbon steel, alkalisation led to passive state and in the same time amphoteric metals could exist in active state. The aim of this work was to clarify usage of monitoring the corrosion rate of amphoteric metals for detection of pH values influenced by cathodic polarisation.
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The influence of the geometry of a longitudinal hollow cathode discharge (HCD) excited in a Cu cathode and He-Ar mixture is studied experimentally and theoretically. Special attention is devoted to the optimization of the HC lengt...
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The influence of the geometry of a longitudinal hollow cathode discharge (HCD) excited in a Cu cathode and He-Ar mixture is studied experimentally and theoretically. Special attention is devoted to the optimization of the HC length to obtain a stable and uniform laser medium with a high excitation efficiency. The influence of the cathode length is demonstrated experimentally by the behaviour of the 780.8 nm Cu ion line. The dependence of the laser power and gain as a function of the cathode length segments is measured. The Plasimo modelling platform is used to construct a model allowing more profound studies of the plasma processes and plasma behaviour under different conditions. Calculations at different cathode lengths are made and typical results such as spatial potential and plasma density distributions are presented and discussed. It is demonstrated that when the cathode length is increased the plasma density at the centre of the cathode decreases and the discharge tends to separate into two independent parts causing axial non-uniformity and reducing the discharge efficiency. The results also suggest that there exist a lower limit of the cathode length. Below this limit an inversion of the axial electric field occurs, which can be regarded as a transition between the conventional and high-voltage HCD under the conditions under study.
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Ba-oxide, Ba-dispenser and Ba-Scandate cathodes have been continuously improved in their emission performance in the past decades. Ba-oxide and Ba-dispenser cathodes are also the dominant types of thermionic cathodes used in most ...
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Ba-oxide, Ba-dispenser and Ba-Scandate cathodes have been continuously improved in their emission performance in the past decades. Ba-oxide and Ba-dispenser cathodes are also the dominant types of thermionic cathodes used in most vacuum tube applications. When improvements in emissive properties are introduced, their impact on cathode life - where several years in a vacuum tube environment are typically required - also needs to be known. Hence, the investigation of cathode life-limiting effects is the basis of accelerated life predictions and of further cathode improvement. In this contribution, the main effects limiting the operating life of Ba/BaO-based thermionic cathodes are discussed, especially related to intrinsic dispensation and resupply to the emissive surface. Emission poisoning induced by adsorption of poisonous gases will not be addressed here. We will stress common points and point out the differences between the three types. (c) 2005 Elsevier B.V. All rights reserved.
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Magnesium metal is a superior anode which has double the volumetric capacity of lithium metal and has a negative reduction potential of -2.37V vs. the standard hydrogen electrode. A major benefit of magnesium is the apparent lack ...
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Magnesium metal is a superior anode which has double the volumetric capacity of lithium metal and has a negative reduction potential of -2.37V vs. the standard hydrogen electrode. A major benefit of magnesium is the apparent lack of dendrite formation during charging which is one of the crucial concerns of using a lithium metal anode. In this Review, we highlight the foremost research in the development of electrolytes and cathodes and discuss some of the significant challenges which must be overcome in realizing a practical magnesium battery.
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