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Experimental study on the similarity of gas discharge in low-pressure Argon gaps

Prijil Mathew, Sajith T. Mathews, Paul Issac, P. J. Kurian

Through experiments and theoretical analysis, we investigated the similarity of gas discharge in low-pressure Argon gaps between two plane-parallel electrodes. We found that the breakdown voltages depended not only on gap length and the product of gas pressure and gap length, but also on the aspect ratio of the gap, i.e. $U_b = f (pd, d/r)$. When we considered similar discharge gaps, the radius $r$, gap length $d$ and gas pressure $p$ fulfilled the conditions of $p_1 r_1 = p_2 r_2$ and $p_1 d_1 = p_2 d_2$ . In this situation the reduced field $E/p$ was also constant. The voltage-current characteristic curves of similar gaps were approximately the same, which is a novel experimental result. Comparison of the discharge physical parameters of the scaled-down gap and prototype gap shows that the proportional relations can be derived from the similarity law. Our experimental results provide some instructions on extrapolating two similar gaps and their discharge properties. Application of the similarity law is straightforward when we scale the discharges up or down if they are too small or large.

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Electronic and Optical Properties of Nickel-Doped Ceria: A Computational Modelling Study

Hussein A. Miran and Zainab N. Jaf

Cerium oxide (CeO2) or ceria has gained increasing interest owing to its excellent catalytic applications. Under the framework of density functional theory (DFT), this contribution demonstrates the role of introducing Nickel (Ni) element into the ceria lattice on the electronic, structural, and optical characterstics. Electronic density of states (DOSs) analysis shows that Ni integration leads to a shrinkage of Ce 4$f$ states and improvement of Ni 3$d$ states in the bottom of conduction band. Furthermore, the calculated optical absorption spectra of Ni-doped CeO2 system shift towards longer visible light and infrared regions when inserting Ni element. Results indicate that Ni-doped CeO2 would decrease the band gap of the system. Finally, Mullikan's charge transfer of Ce[1-x]Ni[x]O2 system exhibits an ionic bond between Ce or Ni and O, and covalent bonds between Ce and Ni atoms. The analysis of absorption spectra demonstrates that Ni-doped CeO2 is potential material to be utilized in photocatalytic, photovoltaic, and solar panels.

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