Laser ablation is a method for fabricating various kinds of nanoparticles including semiconductor quantum dots, carbon nanotubes, nanowires, and core shell nanoparticles. In this method, nanoparticles are generated by nucleation and growth of laser-vaporized species in a background gas. The extremely rapid quenching of vapor is advantageous in producing high purity nanoparticles in the quantum size range (< 10 nm). In this review, the formation mechanism of nanoparticles by laser ablation is summarized. Recent progress on the control of nanoparticle size and the challenges for functional nanoparticle synthesis by advanced laser ablation technology are then discussed.

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In this study, the abrasive size distribution of ceria-based slurry below wafer and its effect on in-wafer uniformity were examined. Based on our observation, the abrasive size varies depending on the location on the wafer. Hence process parameters such as pad surface morphology and slurry viscosity were thoroughly investigated to observe their effect on the distribution on the wafer surface. It was found that the small size particles were considerably reduced near the center location of the wafer surface during the pad lifetime with reduced slurry viscosity and high polishing pressure. Hence, the contact conditions and the characteristic of fluid should be simultaneously considered in order to obtain the stable in-wafer uniformity.

Particulate matter (PM) is one of the major indoor air pollutants in the subway-underground stations in Korea. Various kinds of PM removal methods such as a roll-filter, auto-washable air filter, demister, and electrostatic precipitator are applied in the air handling unit (AHU) of subway station. However, those systems are faced with operation and maintenance problems since the filter-regeneration achieved by air or water jet is often malfunctioned due to the high load of particulates. The filter material also needs periodic replacement. In this study, we designed a novel particle removal system with minimized maintenance requirement compared to above mentioned filter systems. The new system named as panel-type cyclone system was suggested and the key part of the system was developed based on the axial-flow cyclone where the air flow pattern lies on the same axis with air stream through passing the AHU. The shape of axial-flow cyclone was optimized to remove 50% of 2.5 μm-sized particulate matters with minimal pressure drop by using the tool of computational fluid dynamics. We believe that the novel axial-flow cyclone system is cost-effective and efficient way of removing particulate matters in the size range of 1-10 μm in the AHU of subway station or buildings.