Hydrogen hollow cathode ion source

A source of hydrogen ions is disclosed and includes a chamber having at one end a cathode which provides electrons and through which hydrogen gas flows into the chamber. Screen and accelerator grids are provided at the other end of the chamber. A baffle plate is disposed between the cathode and the grids and a cylindrical baffle is disposed coaxially with the cathode at the one end of the chamber. The cylindrical baffle is of greater diameter than the baffle plate to provide discharge impedance and also to protect the cathode from ion flux. An anode electrode draws the electrons away from the cathode. The hollow cathode includes a tubular insert of tungsten impregnated with a low work function material to provide ample electrons. A heater is provided around the hollow cathode to initiate electron emission from the low work function material

Scanning optical pyrometer for measuring temperatures in hollow cathodes

Life-limiting processes in hollow cathodes are determined largely by the temperature of the electron emitter. To support cathode life assessment, a noncontact temperature measurement technique which employs a stepper motor-driven fiber optic probe was developed. The probe is driven inside the hollow cathode and collects light radiated by the hot interior surface of the emitter. Ratio pyrometry is used to determine the axial temperature profile. Thermocouples on the orifice plate provide measurements of the external temperature during cathode operation and are used to calibrate the pyrometer system in situ with a small oven enclosing the externally heated cathode. The diagnostic method and initial measurements of the temperature distribution in a hollow cathode are discussed

Hollow cathode apparatus

A hollow cathode apparatus is described, which can be rapidly and reliably started. An ignitor positioned upstream from the hollow cathode, generates a puff of plasma that flows with the primary gas to be ionized through the cathode. The plasma puff creates a high voltage breakdown between the downstream end of the cathode and a keeper electrode, to heat the cathode to an electron-emitting temperature

Simple, high current LaB_6 cathode

A cathode constructed of a thin, directly heated strip of LaB_6 is described. The cathode is simple to construct, requires modest heating power, has high current emission capability and is quite rugged. Construction details will be given and cathode performance data presented. The cathode has been used in tokamak dc current injection experiments

Nitrogen removal in a two-chambered microbial fuel cell: Establishment of a nitrifying-denitrifying microbial community on an intermittent aerated cathode

A microbial fuel cell (MFC) was used to study nitrogen dynamics and its feasibility for high strength wastewater treatment. Intermittent aeration was applied on the cathode chamber accomplishing the establishment of a simultaneous nitrifying-denitrifying microbial community. A total of 30.4% of the N-NH4 + migrated through the ion exchange membrane being primarily nitrified at the cathode chamber. When intermittent aeration was applied in the cathode, denitrification also occurred achieving 17.8% of nitrate removal without acetate addition, and 41.2% with acetate addition. The microbial community analysis revealed that the nitrification process at the cathode chamber could be explained due to a high predominance of Nitrosomonas sp. as ammonia-oxidising bacteria and other Comamonadaceae phylotypes as potential denitrifiers. Parallel batch denitrification assays, carried out outside the MFC using the cathode effluent, confirmed the existence of heterotrophic denitrification processes with other well known denitrifying dominant phylotypes enrichment (Burkholderiadaceae, Comamonadaceae, Alcaligenaceae).Postprint (author's final draft

Potentialities of the sol-gel route to develop cathode and electrolyte thick layers Application to SOFC systems

In this work, we report the potential of sol–gel process to prepare cathode and electrolyte thin and thick layers on anodic NiO-YSZ supports which were also made from powders prepared by sol–gel route. YSZ and La2 − xNiO4 + δ, La4Ni3O10 were synthesized as electrolyte and cathode materials for SOFC applications. For electrolyte shaping, yttria stabilized zirconia (YSZ, 8% Y2O3) thick films were cast onto porous NiO-YSZ composite substrates by a dip-coating process using a new suspension formulation. Part of the YSZ precursor colloidal sol was added in the suspension to ensure both homogeneity and adhesion of the electrolyte on the anodic substrate after thermal treatment at 1400 °C for 2 h. By precisely controlling the synthesis parameters, dense and gas-tight layers with thicknesses in the range of 10–20 μm have been obtained. Gas-tightness was confirmed by He permeation measurements. Concerning cathode processing, a duplex microstructured cathode consisting of both La2 − xNiO4 + δ ultra-thin films (few nanometers) and La2 − xNiO4 + δ and/or La4Ni3O10 thick layers (few micrometers) was prepared on YSZ substrates by the dip-coating process, with the thickness being dependent on the nature of the dip-coated solution (polymeric sol or adequate suspension). The derived cathode microstructure, related to the number/thickness of layers and type of architecture, was correlated to the good cell electrochemical performances. Concerning cathode processing, a duplex microstructured cathode consisting of both La2 ? xNiO4 + ? ultra-thin films (few nanometers) and La2 ? xNiO4 + ? and/or La4Ni3O10 thick layers (few micrometers) was prepared on YSZ substrates by the dip-coating process, with the thickness being dependent on the nature of the dip-coated solution (polymeric sol or adequate suspension). The derived cathode microstructure, related to the number/thickness of layers and type of architecture, was correlated to the good cell electrochemical performances

Endurance testing of downstream cathodes on a low-power MPD thruster

A low-power MPD thruster with downstream cathode was tested for endurance with a series of hollow cathode designs. Failure modes and failure mechanisms were identified. A new hollow cathode (with rod inserts) has emerged which shows promise for long life. The downstream positioning of the cathode was also changed from an on-axis location to an off-axis location. Data are presented for a 1332-hour life test of this new hollow cathode located at the new off-axis location. Xenon propellant was used

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Department of Energy Engineering (Energy Engineering)Solid oxide fuel cells (SOFCs) are recognized as next generation environmentally friendly energy conversion devices due to their high energy conversion efficiency, fuel flexibility, efficient reclamation of waste heat, and low pollutant emissions. Nevertheless, the commercialization of SOFCs has been impeded by reason of some issues associated with the high operating temperatures (800-1000oC) such as undesired reactions between cell components, high cost, and material compatibility challenges. Thus, reducing the operating temperatures toward an intermediate temperature range (600-800oC) is essential to overcome the aforementioned problems. In intermediate temperature SOFCs (IT-SOFCs), however, electrocatalytic activity toward oxygen reduction reaction at the cathode is significantly decreased, which in turn causes insufficient fuel cell performance. Current researches, therefore, have been focused on enhancing the performance of cathode for effective IT-SOFC operation. In this regard, the infiltration method could be an excellent cathode fabrication method, considering its outstanding advantages toward intermediate temperature operation. First, each optimized sintering temperature of cathode and electrolyte can be applied, ensuring the favorable characteristics for IT-SOFC operation. Second, due to relatively low sintering temperature, nano structured cathodes can be formed, resulting in enlarged surface area and enhancement of electrochemical performance. Finally, long term stability is improved because the thermal expansion coefficient between cathode and electrolyte is minimized. This thesis mainly focuses on the fabrication of SOFC cathode by the infiltration method to achieve high fuel cell performance in the intermediate temperature range. Herein, my research paper studying infiltrated cathode materials for IT-SOFC is presented as follows. - A Nano-structured SOFC Composite Cathode Prepared via Infiltration of La0.5Ba0.25Sr0.25Co0.8Fe0.2O3-?? into La0.9Sr0.1Ga0.8Mg0.2O3-?? for Extended Triple Phase Boundary Areaclos

Prevention of cathode damage from positive ion bombardment

Mixed alkaline earth oxide compounds deposited into hole at cathode surface center prevent ion back bombardment damage to cathode by reducing oxide layer and by creating metallic diffusion along sides of hole for enhanced electron emission