Effect of cathode surface area and separately stabilized cathodes on high power glow discharges for CO2laser excitation

1988 ◽  
Vol 63 (5) ◽  
pp. 1363-1366 ◽  
Author(s):  
D. R. Evans ◽  
J. E. Harry
Keyword(s):  
Surface Area ◽  
High Power ◽  
Cathode Surface ◽  
Glow Discharges

scholarly journals Electrochemical Performance of Aluminum Doped Ni1−xAlxCo2O4 Hierarchical Nanostructure: Experimental and Theoretical Study

Processes ◽  
2021 ◽  
Vol 9 (10) ◽  
pp. 1750
Author(s):  
Deepa Guragain ◽  
Romakanta Bhattarai ◽  
Jonghyun Choi ◽  
Wang Lin ◽  
Ram Krishna Gupta ◽  
...  
Keyword(s):  
Energy Density ◽  
Electrochemical Performance ◽  
Band Gap ◽  
Specific Capacitance ◽  
Surface Area ◽  
Power Density ◽  
High Power ◽  
Energy Band ◽  
High Specific Capacitance ◽  
High Power Density

For electrochemical supercapacitors, nickel cobaltite (NiCo2O4) has emerged as a new energy storage material. The electrocapacitive performance of metal oxides is significantly influenced by their morphology and electrical characteristics. The synthesis route can modulate the morphological structure, while their energy band gaps and defects can vary the electrical properties. In addition to modifying the energy band gap, doping can improve crystal stability and refine grain size, providing much-needed surface area for high specific capacitance. This study evaluates the electrochemical performance of aluminum-doped Ni1−xAlxCo2O4 (0 ≤ x ≤ 0.8) compounds. The Ni1−xAlxCo2O4 samples were synthesized through a hydrothermal method by varying the Al to Ni molar ratio. The physical, morphological, and electrochemical properties of Ni1−xAlxCo2O4 are observed to vary with Al3+ content. A morphological change from urchin-like spheres to nanoplate-like structures with a concomitant increase in the surface area, reaching up to 189 m2/g for x = 0.8, was observed with increasing Al3+ content in Ni1−xAlxCo2O4. The electrochemical performance of Ni1−xAlxCo2O4 as an electrode was assessed in a 3M KOH solution. The high specific capacitance of 512 F/g at a 2 mV/s scan rate, 268 F/g at a current density of 0.5 A/g, and energy density of 12.4 Wh/kg was observed for the x = 0.0 sample, which was reduced upon further Al3+ substitution. The as-synthesized Ni1−xAlxCo2O4 electrode exhibited a maximum energy density of 12.4 W h kg−1 with an outstanding high-power density of approximately 6316.6 W h kg−1 for x = 0.0 and an energy density of 8.7 W h kg−1 with an outstanding high-power density of approximately 6670.9 W h kg−1 for x = 0.6. The capacitance retention of 97% and 108.52% and the Coulombic efficiency of 100% and 99.24% were observed for x = 0.0 and x = 0.8, respectively. First-principles density functional theory (DFT) calculations show that the band-gap energy of Ni1−xAlxCo2O4 remained largely invariant with the Al3+ substitution for low Al3+ content. Although the capacitance performance is reduced upon Al3+ doping, overall, the Al3+ doped Ni1−xAlxCo2O4 displayed good energy, powder density, and retention performance. Thus, Al3+ could be a cost-effective alternative in replacing Ni with the performance trade off.

scholarly journals Time evolution of the two-dimensional expansion velocity distributions of the cathode plasma in pulsed high-power diodes

2013 ◽  
Vol 31 (1) ◽  
pp. 129-134 ◽  
Author(s):  
Jie Yang ◽  
Ting Shu ◽  
Yuwei Fan
Keyword(s):  
High Power ◽  
Cathode Surface ◽  
Transverse Velocity ◽  
Longitudinal Velocity ◽  
Expansion Velocity ◽  
Two Dimensional ◽  
Plasma Expansion ◽  
Cathode Plasma ◽  
Power Diodes ◽  
Diode Current

AbstractA combination of electrical and optical diagnostics has been used to investigate the time evolution of the two-dimensional expansion velocity distributions of the cathode plasma in pulsed high-power diodes. The perveance model based on the Child-Langmuir law was used to calculate the expansion velocity of the diode plasmas from voltage and current profiles. Additionally, a four-channel high speed framing camera was used to observe the formation and subsequent movement of the cathode plasma. More accurate and valuable information about the dynamics of the cathode plasma was also acquired by utilizing the digital image processing methods. Results from the experiments and theoretical analysis were compared. In this paper, the experiments have been performed using a high-voltage pulse generator with 200 kV output voltage and 110 ns pulse duration. Current densities up to 440 A/cm2were produced. The observation of the cathode plasma expansion in transverse direction indicated that the diode current was cathode-limited in the current rising stage (the first 60 ns of the current pulse). The perveance model should be modified taking in account the time dependent expanding plasma surface (i.e., not the whole cathode surface) for this period. The velocity in the direction parallel to the cathode surface (transverse velocity) was much larger than that in the direction perpendicular to the cathode surface (longitudinal velocity), and further, it dropped from 90 cm/μs to nearly 20 cm/μs rapidly. It was shown that, during the current flattop stage, the plasma filled out all the surface of cathode and the diode current was space-charge-limited. The values of the transverse velocity and longitudinal velocity were nearly the same and decreased relatively slowly. The satisfactory coincidence of experimental and calculated (both were in the range of 6–8 cm/μs) values of the cathode plasma expansion velocities was obtained.

scholarly journals Electron Multiplier Tube of Large Effective Cathode Surface Area

Nature ◽  
1948 ◽  
Vol 161 (4080) ◽  
pp. 60-60 ◽  
Author(s):  
P. S. FARAGÓ
Keyword(s):  
Surface Area ◽  
Cathode Surface ◽  
Electron Multiplier

scholarly journals Effect of specific cathode surface area on biofouling in an anaerobic electrochemical membrane bioreactor: Novel insights using high-speed video camera

2019 ◽  
Vol 577 ◽  
pp. 176-183 ◽  
Author(s):  
Veerraghavulu Sapireddy ◽  
Ala’a Ragab ◽  
Krishna P. Katuri ◽  
Yuanlie Yu ◽  
Zhiping Lai ◽  
...  
Keyword(s):  
Surface Area ◽  
High Speed ◽  
Membrane Bioreactor ◽  
Cathode Surface ◽  
Video Camera ◽  
High Speed Video ◽  
High Speed Video Camera

scholarly journals Investigation and Improvement of Scalable Oxygen Reducing Cathodes for Microbial Fuel Cells by Spray Coating

Processes ◽  
2019 ◽  
Vol 8 (1) ◽  
pp. 11 ◽  
Author(s):  
Thorben Muddemann ◽  
Dennis Haupt ◽  
Bolong Jiang ◽  
Michael Sievers ◽  
Ulrich Kunz
Keyword(s):  
Fuel Cells ◽  
Surface Area ◽  
Power Density ◽  
Microbial Fuel Cells ◽  
Cathode Surface ◽  
Weight Ratio ◽  
Strong Increase ◽  
Coating Quality ◽  
Catalyst Coating

This contribution describes the effect of the quality of the catalyst coating of cathodes for wastewater treatment by microbial fuel cells (MFC). The increase in coating quality led to a strong increase in MFC performance in terms of peak power density and long-term stability. This more uniform coating was realized by an airbrush coating method for applying a self-developed polymeric solution containing different catalysts (MnO2, MoS2, Co3O4). In addition to the possible automation of the presented coating, this method did not require a calcination step. A cathode coated with catalysts, for instance, MnO2/MoS2 (weight ratio 2:1), by airbrush method reached a peak and long-term power density of 320 and 200–240 mW/m2, respectively, in a two-chamber MFC. The long-term performance was approximately three times higher than a cathode with the same catalyst system but coated with the former paintbrush method on a smaller cathode surface area. This extraordinary increase in MFC performance confirmed the high impact of catalyst coating quality, which could be stronger than variations in catalyst concentration and composition, as well as in cathode surface area.

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