Low temperature plasma as a means to transform nanoparticle atomic structure

Üner, Necip Berker
Thimsen, E.
Low temperature plasma (LTP) is a highly nonequilibrium substance capable of increasing the specific free energy of mass that flows through it. Despite this attractive feature, there are few examples of the transformation of solid material with an equilibrium atomic structure into a material with a nonequilibrium atomic structure. As a proposed example of such a transformation, in this work, it is argued that the transformation of crystalline metal nanoparticles into amorphous metal nanoparticles is feasible using LTP. To inform the feasibility calculations, detailed characterization was performed to determine the electron temperature, ion density, and background gas temperature as a function of axial position in a typical flow-through, radiofrequency, capacitively-coupled plasma reactor. Measurements revealed the existence of an intense zone with sharply elevated ion density and gas temperature in the vicinity of the powered electrode. The high intensity zone, amidst an otherwise low-intensity plasma, provides a means by which to transform the atomic structure of nanoparticles while maintaining unipolar negative charge to suppress coagulation. Theory suggests that such an intense zone would provide intense heating of nanoparticles, and subsequent rapid cooling. Calculations for copper-zirconium (CuZr) alloy show that the temperature history of a nanoparticle depends primarily on the intensity of the zone in the vicinity of the powered electrode, and on particle size. If one considers melting CuZr nanoparticles in the intense zone and then rapidly cooling them in the low-intensity plasma downstream, then the quenching rates are found to be high, on the order of 10(5) K s(-1). Since quenching rates of this magnitude are sufficient to arrest an amorphous atomic structure, LTP reactors can be used to transform crystalline metal nanoparticles into amorphous metal nanoparticles via a highly nonequilibrium quenching process.


High temperature proton exchange membrane fuel cells
Ergün, Dilek; Eroğlu, İnci; Department of Chemical Engineering (2009)
It is desirable to increase the operation temperature of proton exchange membrane fuel cells above 100oC due to fast electrode kinetics, high tolerance to fuel impurities and simple thermal and water management. In this study; the objective is to develop a high temperature proton exchange membrane fuel cell. Phosphoric acid doped polybenzimidazole membrane was chosen as the electrolyte material. Polybenzimidazole was synthesized with different molecular weights (18700-118500) by changing the synthesis condi...
Low temperature photocatalytic oxidation of carbon monoxide over palladium doped titania catalysts
Yetişemiyen, Pelin; Karakaş, Gürkan; Department of Chemical Engineering (2010)
The room temperature photocatalytic oxidation of carbon monoxide in excess air was examined over silica/titania and 0.1%palladium/silica/titania catalysts under UV irradiation. The experiments were conducted in batch re-circulated reactor with the initial 1000 ppm carbon monoxide in air and 0.5 g catalyst charge and the conversion of carbon monoxide to carbon dioxide was followed by FT-IR spectro-photometer. The change in gas composition in dark and under 36 Watts of UV irradiation exposed to a catalyst are...
High gradient plasma waves to accelerate charged particles
Yedierler, Burak; Bilikmen, Kadri Sinan; Department of Physics (2002)
In this thesis one of the most promising plasma based particle acceleration methods, the Laser Wakefield Acceleration (LWFA) mechanism is discussed in detail. Starting from the standard LWFA method, the wakefield generation in plasmas and the energy gain of electrons are formulated. The wakefield generation by a multi passage laser beam in a plasma model based on the resonant LWFA is proposed. The growth of the wakefield amplitude is demonstrated and the corresponding energy gain of electrons is calculated....
High temperature microstructural stability and recrystallization mechanisms in 14YWT alloys
Aydoğan Güngör, Eda; Takajo, S.; Vogel, S. C.; Maloy, S. A. (Elsevier BV, 2018-04-01)
In-situ neutron diffraction experiments were performed on room temperature compressed 14YWT nanostructured ferritic alloys at 1100 degrees C and 1150 degrees C to understand their thermally activated static recrystallization mechanisms. Existence of a high density of Y-Ti-O rich nano-oxides ( and {112} texture components during annealing, in contrast to the conventional recrystallization textures in body centered cubic alloys. Furthermore, nano-oxide size, shape, density and distribution are considerably di...
High-energy particle acceleration in the shell of a supernova remnant
Aharonian, FA; et. al. (2004-11-04)
A significant fraction of the energy density of the interstellar medium is in the form of high-energy charged particles ( cosmic rays)(1). The origin of these particles remains uncertain. Although it is generally accepted that the only sources capable of supplying the energy required to accelerate the bulk of Galactic cosmic rays are supernova explosions, and even though the mechanism of particle acceleration in expanding supernova remnant (SNR) shocks is thought to be well understood theoretically(2,3), un...
Citation Formats
N. B. Üner and E. Thimsen, “Low temperature plasma as a means to transform nanoparticle atomic structure,” PLASMA SOURCES SCIENCE & TECHNOLOGY, vol. 27, no. 7, pp. 0–0, 2018, Accessed: 00, 2022. [Online]. Available: https://hdl.handle.net/11511/97036.