Now showing 1 - 10 of 18
  • Publication
    Metadata only
    Evidence of the ionization instability and ion acoustic turbulence correlation in sub-ampere hollow cathodes
    (2022)
    Potrivitu, George-Cristian
    ;
    Plasma instabilities in the plume of hollow cathodes have been extensively researched in particular for high-current operation. The rise of plume mode ionization-like instability leads to a degradation of cathode’s performance along with the emergence of highly energetic ions that can produce sputtering of various cathode’s surfaces. Numerical simulations using 2D fluid or hybrid codes brought forward an interesting correlation between the evolution of ion acoustic turbulence (IAT) and emergence of plume mode oscillations. Such numerical findings were proven to be true by experimental measurements of wave dispersion and plume mode-IAT correlation in the plume of cathodes emitting currents >10 A. This study brings forward evidence of the correlation between plume mode oscillations and IAT in the plume of low-current cathodes operating with Kr at sub-ampere current levels. It is shown that at <1 A the plume mode instability is highly correlated with the IAT and the anomalous electron collision drives the electron transport in the cathode plume. The fluctuations in IAT wave energy lead to large temperature oscillations which then drive fluctuations in the density via ionization.
      38
  • Publication
    Open Access
    How to survive at point nemo? Fischer–Tropsch, artificial photosynthesis, and plasma catalysis for sustainable energy at isolated habitats
    (Wiley, 2023)
    Levchenko, Igor
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    ;
    Baranov, Oleg
    ;
    Bazaka, Kateryna
    Inhospitable, inaccessible, and extremely remote alike the famed pole of inaccessibility, aka Point Nemo, the isolated locations in deserts, at sea, or in outer space are difficult for humans to settle, let alone to thrive in. Yet, they present a unique set of opportunities for science, economy, and geopolitics that are difficult to ignore. One of the critical challenges for settlers is the stable supply of energy both to sustain a reasonable quality of life, as well as to take advantage of the local opportunities presented by the remote environment, e.g., abundance of a particular resource. The possible solutions to this challenge are heavily constrained by the difficulty and prohibitive cost of transportation to and from such a habitat (e.g., a lunar or Martian base). In this essay, the advantages and possible challenges of integrating Fischer–Tropsch, artificial photosynthesis, and plasma catalysis into a robust, scalable, and efficient self-contained system for energy harvesting, storage, and utilization are explored.
      10  18
  • Publication
    Restricted
    Teaching physics using an IT tool
    (1998)
    Information technology is a critical element in teaching and learning and is central to our mission of preparing students for the 21St century. This work explores the use and benefit of computer aided techniques in undergraduate physics teaching. It is demonstrated that the computer aided teaching techniques indeed promote students' deep learning and critical thinking skills, especially for undergraduate theoretical and experimental physics courses. The results show that such a non-conventional approach provides a great opportunity to effectively motivate students in understanding some abstractive physical concepts and principles.
      158  11
  • Publication
    Open Access
    Nanoengineered carbon-based interfaces for advanced energy and photonics applications: A recent progress and innovations
    (2022)
    Levchenko, Igor
    ;
    Baranov, Oleg
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    Riccardi, Claudia
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    Roman, H. Eduardo
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    Cvelbar, Uros
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    Ivanova, Elena P.
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    Mohandas, Mandhakini
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    Scajev, Patrik
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    Malinauskas, Tadas
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    ;
    Bazaka, Kateryna
    As famed quantum physicist W. Pauli once said, “The surface was invented by the devil”. The nonequilibrium state of particles forming the surface, and the presence of dangling bonds transform the surfaces into a 2D reactor with high physical and chemical reactivity. When two such active surfaces are matched, their interface becomes even more reactive, giving rise to novel properties or enhanced performance. For this reason, much effort is applied to design nanoengineered interfacial systems for applications spanning all facets of human life. This review article discusses recent, mostly within two years, progress in the design of complex, sophisticated carbon-based interfacial material systems for energy and photonics applications, with the aim to emphasize some of the most interesting and important examples of such systems. Differences in the processes that take place on flat and 3D (curved) surfaces are discussed, with the view of guiding the design and construction of complex functional interfaces, focusing on several points that are of particular importance to the ongoing development of advanced interfacial material systems.
    WOS© Citations 5Scopus© Citations 7  55  92
  • Publication
    Open Access
    Ultra-low reflective silicon surfaces for photovoltaic applications
    (2016)
    Lim, Mark Jian Wei
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    Huang, Shiyong
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    Chan, Chia Sern
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    Wei, Deyuan
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    Guo, Yingnan
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    Xu, Luxiang
    ;
    Ostrikov, Kostya (Ken)
    Silicon based photovoltaic cells still remain a mainstay in the industries due to its relatively low cost for manufacturing and implementation. A good knowledge base of the material has also been built up over the years and there is no doubt that silicon based photovoltaic cells would continue to lay the basis for renewable energy for many years to come. However, it is widely known that conventional silicon photovoltaic cells have relatively lower power conversion efficiencies as compared to its next generation counterparts. This is partly due to the high optical losses on surfaces, resulting in poor harvesting of energy from incident light. In this work, an ICP process was developed to fabricate ultra-low reflective silicon surfaces for photovoltaic applications. An Ar + H2 feedstock was used to texture nanocones on the surface of silicon wafers, reducing the reflective losses and forming a high quality pn junction simultaneously. Reflectivity of the samples were characterised with a Zolix SCS10-X150-DSSC UV-Vis spectrometer with an attached integrating sphere, while the photovoltaic properties were measured with a PV characterization suite from Sinton instruments. The low reflectivity with promising electronic properties of the processed materials shows propitious potential for applications in the field of photovoltaics.
    WOS© Citations 2Scopus© Citations 2  164  183
  • Publication
    Open Access
    Discharge mode transition in a Krypton-fed 1 A-class LaB6 cathode for lowpower Hall thrusters for small satellites
    (2020)
    Potrivitu, George-Cristian
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    Xu, L.
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    Huang, Shih-Hao
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    Mohd Rohaizat Abdul Wahab
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    Thermionic cathodes are essential for the operation of various electrostatic propulsion devices. They strongly influence the performance and lifetime of the propulsion system. In this study, a 1 A-class LaB6 laboratory model hollow cathode has been tested with krypton in diode and triode configurations in order to assess for the cathode discharge mode transition behavior. Measurements have been performed over a range of krypton mass flow rates (0.1, 0.15 and 0.21 mg/s, or 1.6, 2.4 and 3.4 sccm), keeper (0.1, 0.15, 0.2 A) and anode currents (0.1 to 1 A) at a fixed cathode-to- anode distance. Seven criteria were used to distinguish between the spot and plume mode operations. The results show that the mode transition in low-current cathodes may be a non-linear phenomenon and only some of the existing mode transition criteria can be used to accurately predict the spot/plume discharge regions at low emission currents.
    WOS© Citations 17Scopus© Citations 17  57  137
  • Publication
    Open Access
    High quality hydrogenated amorphous silicon thin films with enhanced growth rates for surface passivation in an Al2O3 based ICP reactor
    (2016)
    Lim, Mark Jian Wei
    ;
    Chan, Chia Sern
    ;
    Xu, Luxiang
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    Ong, T. M.
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    Huang, Shiyong
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    Wei, Deyuan
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    Guo, Yingnan
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    Plasma processing of materials in low frequency inductively coupled plasma (LF-ICP) reactors has limitations involving the presence of contaminant species found in the discharge. It has been shown in previous work through optical emission spectroscopy that a main source of contaminants were oxygen related species which were not part of the feedstock recipe. In this work, amorphous silicon thin films were grown on silicon substrates with a LF-ICP reactor. The dielectric top lid plays an important role in the reduction of oxygen species detected in the thin films. It was postulated that the source of the contaminants came from sputtering of the lids. The replacement of the conventional quartz (SiO2) lid with that of alumina (Al2O3) reduced the oxygen species present in the resulting discharge, which is often a source of contamination in the resulting thin films, impinging the passivation grade of the resulting films. The modified reactor configuration also resulted in increased hydrogenation and deposition rate of the thin films. The results show that alumina lids serve as a promising alternative in replacing the conventional quartz lids in LF-ICP reactors for materials processing, resulting in efficient power transfer to the plasma and films which are rid of contaminant species.
    WOS© Citations 3Scopus© Citations 3  370  233
  • Publication
    Open Access
    Precise calibration of propellant flow and forces in specialized electric propulsion test system
    (2018)
    Lim, Mark Jian Wei
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    Huang, Shiyong
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    Sun, Yufei
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    Lu, Luxiang
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    Sim, Roysmond Zhen Wei
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    Yee, Jen Siong
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    Zhang, Zhonglin
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    Levchenko, Igor
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    Precise readout values for propellant flow rates obtained from mass flow controllers are vital for derivation of accurate and reliable figures that are indicative of thruster performance, such as the specific impulse and thruster effi-ciency. This is exceptionally important in thrusters employed for micro-propulsion for orbit maintenance and drag compen-sation in small satellites, where a small uncertainty and devia-tion in propellant flow would lead to large errors in derived values. Therefore, it is crucial for researchers engaged in pro-pulsion-based research to ensure that their gas flow controllers are calibrated and verified experimentally to be accurate be-fore engaging in thorough experimental work. In this work, an experimental method for the practical calibration of propellant feed systems in typical Hall thruster setups is tested. Results yield reliable calibration factors that have been applied for performance correction of miniature Hall thrusters. The cor-rected propellant flows correlate well with obtained ionization oscillation waveforms, indicating that the presented method for calibration is favorable and dependable for application to ground test facilities for thrust performance qualification.
    WOS© Citations 5Scopus© Citations 8  338  278
  • Publication
    Open Access
    Structural, electronic, and optical properties of wurtzite and rocksalt InN under pressure
    (2010)
    Duan, Man-Yi
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    He, Lin
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    Xu, Ming
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    Xu, Ming-Yao
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    Ostrikov, Kostya (Ken)
    Structural stability, electronic, and optical properties of InN under high pressure are studied using the first-principles calculations. The lattice constants and electronic band structure are found consistent with the available experimental and theoretical values. The pressure of the wurtzite-to-rocksalt structural transition is 13.4 GPa, which is in an excellent agreement with the most recent experimental values. The optical characteristics reproduce the experimental data thus justifying the feasibility of our theoretical predictions of the optical properties of InN at high pressures.
    WOS© Citations 17Scopus© Citations 16  155  150
  • Publication
    Open Access
    Lightning under water: Diverse reactive environments and evidence of synergistic effects for material treatment and activation
    (2018)
    Levchenko, Igor
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    Bazaka, Kateryna
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    Baranov, Oleg
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    Sankaran, R. Mohan
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    Nomine, Alexandre
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    Belmonte, Thierry
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    This focused review aims to reveal and illustrate some unique features of processes triggered by high-density energy applied to liquids and gas-liquid interfaces and to highlight a wide spectrum of their technological applications capable of producing various advantageous effects, ranging from nanosynthesis to biological and medical applications. Plasma, electric discharges, laser, and ultrasound power effects were selected as representative examples of high-density energy and liquid interactions, yet the available possibilities are not limited by these quite different types of power and thus the reader could extrapolate the outlined features and effects to other kinds of powerful impacts. The basic physical mechanisms are briefly reviewed with the aim to familiarize the readers with the potential capabilities of high-density energy processes in liquids. These will be of direct interest to researchers tasked with the development, optimization, and characterization of processes and highly reactive environments for highly controlled transformation of matter in abiotic and biological systems. It could also be highly useful for under- and post-graduate students specializing in the related fields and general physical audience involved in various plasma, materials, energy conversion, and other concurrent research activities.
    WOS© Citations 42Scopus© Citations 50  174  196