tailieunhanh - Báo cáo hóa học: " Micro-nano hybrid structures with manipulated wettability using a two-step silicon etching on a large area"

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Micro-nano hybrid structures with manipulated wettability using a two-step silicon etching on a large area | Kim et al. Nanoscale Research Letters 2011 6 333 http content 6 1 333 o Nanoscale Research Letters a SpringerOpen Journal NANO EXPRESS Open Access Micro-nano hybrid structures with manipulated wettability using a two-step silicon etching on a large area Beom Seok Kim Sangwoo Shin Seung Jae Shin Kyung Min Kim and Hyung Hee Cho Abstract Nanoscale surface manipulation technique to control the surface roughness and the wettability is a challenging field for performance enhancement in boiling heat transfer. In this study micro-nano hybrid structures MNHS with hierarchical geometries that lead to maximizing of surface area roughness and wettability are developed for the boiling applications. MNHS structures consist of micropillars or microcavities along with nanowires having the length to diameter ratio of about 100 1. MNHS is fabricated by a two-step silicon etching process which are dry etching for micropattern and electroless silicon wet etching for nanowire synthesis. The fabrication process is readily capable of producing MNHS covering a wafer-scale area. By controlling the removal of polymeric passivation layers deposited during silicon dry etching Bosch process we can control the geometries for the hierarchical structure with or without the thin hydrophobic barriers that affect surface wettability. MNHS without sidewalls exhibit superhydrophilic behavior with a contact angle under 10 whereas those with sidewalls preserved by the passivation layer display more hydrophobic characteristics with a contact angle near 60 . Introduction In general boiling heat transfer is considered to be very effective mechanism for cooling the high heat-generating devices due to the large latent heat by phase transition accompanied by fast transport of gas-phased bubbles. In many industrial fields related to energy conversion . nuclear power plants heat pump and electronics improving the performance of boiling heat transfer based on surface treatment and .