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Tham khảo tài liệu 'silicon carbide materials processing and applications in electronic devices part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 165 SiC from Amorphous to Nanosized Materials the Exemple of SiC Fibres Issued of Polymer Precursors the crystallization. The first problem to solve Table 1 was the way to establish the bridge between the polymeric Si-C n chains i the first route NLMTM Nippon Carbon fibre Ishikawa 1995 is the thermal oxidation Si-O-Si bridge at relatively low temperature 200 C the resulting SiO2 content decreases from 25 to 10 wt with improvements ii the second one is the electronic irradiation that allows forming Si-C bridges but leads to a carbon excess C Si 1.4 in Hi-NicalonTM Nippon Carbon fibre Berger et al 1995 idem 1999 alternatively the grafting of Ti or Zr alkoxide Ti or Zr addition leads to rather similar material but the fibres could be made with smaller diameter UBE Industries TyrannoTM LOX-M ZE and TE grade fibres Berger et al. 1997 idem 1999 iii the optimization of the organic precursor and associated thermal treatments gives stoichiometric SiC fibre SA3TM Ube Industries SylramicTM Dow Corning Corp. Fibres and Hi-NicalonTM Type S Lipowitz et al. 1995 Ishikawa et al. 1998 Berger et al. 1999 Bunsell Piant 2006 . The high temperature of the manufacture process leads to much larger grain sizes. Generation 1st 2nd 3rd Producer Nippon Carbon Nippon Carbon Ube Industries Ube Industries Dow Corning Corp. Nippon Carbon Grade NLM Nicalon Hi-Nicalon ZE TE SA3 SYLRAMIC Hi-S Reticulation Si-O Electron Electron Si-O bond Si-O Electron bond irradiation irradiation bond irradiation Grain size nm 2 5-10 5-10 50 50 50 Si C stoichiometry 1.3 1.3 1.3 1 1 1 Diameter pm - 3 15 12 11 7.5 10 12 Table 1. Small diameter SiC fibre generations. The first generations fibre microstructures consist of an amorphous ternary phase made of SiOxCy tetrahedra Porte Sartre 1989 with x y 4 with 1.4-1.7 nm SiC crystallites and 5 of randomly oriented free carbon aggregates 1 nm in size NicalonTM 200 grade x 1.15 . Carbon 002 lattice fringe images showed small stacks of two fringes of around 0.7 nm in size .
