Dusty Plasmas in Supercritical Carbon Dioxide

Dusty plasmas, which are systems comprising plasmas and dust particles, have emerged in various fields such as astrophysics and semiconductor processes. The fine particles possibly form ordered structures, namely, plasma crystals, which have been extensively studied as a model to observe statistical phenomena. However, the structures of the plasma crystals in ground-based experiments are two-dimensional (2D) because of the anisotropy induced by gravity. Microgravity experiments successfully provided opportunities to observe the novel phenomena hidden by gravity. The dusty plasmas generated in supercritical fluids (SCFs) are proposed herein as a means for realizing a pseudo-microgravity environment for plasma crystals. SCF has a high and controllable density; therefore, the particles in SCF can experience pseudo-microgravity conditions with the aid of buoyancy. In this chapter, a study on the particle charging and the formation of the plasma crystals in supercritical CO2, the realization of a pseudo-microgravity environment, and the outlook for the dusty plasmas in SCF are introduced. Our studies on dusty plasmas in SCF not only provide the pseudo-microgravity conditions but also open a novel field of strongly coupled plasmas because of the properties of media

Defects in ZnO nanoparticles laser-ablated in water-ethanol mixtures at different pressures

The effect of liquid medium and its pressure on the photoluminescence of ZnO nanoparticles prepared via laser ablation of Zn targets in various water-ethanol mixtures is studied. As the ethanol content increases, the photoluminescence of the product changes, while metallic zinc is observed to emerge in nanomaterials prepared in ethanol-rich environments. The applied pressure had a less profound effect, mainly affecting materials produced in water or water-ethanol, and much less those generated in pressurized ethanol. Tuning the reactivity of the liquid and pressurizing it during laser ablation is demonstrated to be promising for tailoring the emission properties of the product

ZnO nanorods prepared via ablation of Zn with millisecond laser in liquid media

ZnO nanomaterials with controlled size, shape and surface chemistry are required for applications in diverse areas, such as optoelectronics, photocatalysis, biomedicine and so on. Here, we report on ZnO nanostructures with rod-like and spherical shapes prepared via laser ablation in liquid using a laser with millisecond-long pulses. By changing laser parameters (such as pulse width and peak power), the size or aspect ratio of such nanostructures could be tuned. The surface chemistry and defects of the products were also strongly affected by applied laser conditions. The preparation of different structures is explained by the intense heating of liquid media caused by millisecond-long pulses and secondary irradiation of already-formed nanostructures

Optical emission spectroscopy of atmospheric-pressure non-equilibrium plasma with mist injection

This paper describes optical emission spectroscopic diagnostics of atmospheric-pressure non-equilibrium plasma with mist injection. Electron number densities and gas temperatures are estimated from Hβ (486 nm) and OH (309 nm) spectra to be on the order of 1015 cm-3 and 440–540 K, respectively, for the conditions tested in this study. Comparison of the rotational temperatures of N2 and OH indicates that two-temperature analysis of OH rotational spectra provides gas temperature even with mist injection

Rapid breakdown mechanisms of open air nanosecond dielectric barrier discharges

Tsuyohito Ito, Tatsuya Kanazawa, and Satoshi Hamaguchi, Physical Review Letters 107, 065002, 201

Structure of laboratory ball lightning

Tsuyohito Ito, Tomoya Tamura, Mark A. Cappelli, and Satoshi Hamaguchi, Physical Review E 80, 067401, 200

Silent elongation of polyrotaxane and its composites

Polyrotaxanes (PR) have attracted great interest due to their unique mechanical properties, exhibiting the pulley effect, via their slide-ring topological structure. Flexible and functional composite materials consisting of PR and inorganic particles, particularly those with plasma-surface modifications, have also shown higher toughness, even with large amounts of inorganic particles present. In this study, we verified the effect of neat PR and its composites with graphene nanoplates or carbon nanofibers by measuring acoustic emission (AE). Simultaneous AE and tensile measurements were tested several times for each sample, and AE signals during elongation were acquired. It revealed that the conventional fixed cross-linked elastomer materials showed AE signals in the entire tensile region, while the movable-cross-linked materials of PR showed almost no AE signal counts. This suggests that neat PR had almost no microscopic fracture before final breakage via the pulley effect. PR composites with plasma-surface-modified fillers showed a lower number of AE signals than that with unmodified fillers. This might be due to the surface modification of fillers, which improved filler dispersibility and/or prevented a large drop in the mobility of cross-linking points