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Journal of the Korean Ceramic Society Vol. 44, No. 2, pp. 93~97, 2007. Preparation of High Purity Si Powder by SHS Chang Yun Shin, Hyun Hong Min, Ki Seok Yun, and Chang Whan Won Engineering Research Center for Rapidly Solidified Materials, Chungnam National University, Daejeon 305-764, Korea (Received November 13, 2006; Accepted January 8, 2007) w w š g Á xyá» Á y û w š (2006 11 13 ; 2007 1 8 ) ABSTRACT High purity Si powder was prepared in the system of SiO 2 -Mg combustion reaction. Various conditions of combustion reaction and leaching were investigated. As the particle size of Mg decreased and the compaction pressure increased the quantity of the unreacted powder was decreased. In the acid leaching of MgO, increasing particle size, reaction temperature, rotating speed and reaction time made leaching effect low. Final Si powder produced by combustion and leaching reaction, has a high purity of 99.9% with irregular shape. Key words : Combustion, Leaching, Silicon, SiO 2, SHS 1. wš w g ƒ š w. p g ƒ ƒ g w 4XXX w v ƒ w, y j wš. w w» VTR head drum ƒ»» t g š. wš p»» xyƒ š g»q z w j g. š g» w š g w. 1-3) š g w y g y ù 3 y y w g ù ƒ ƒw œw» j z w. x ù wš w w. ü» y y y Corresponding author : Chang Whan Won E-mail : cwwon@cnu.ac.kr Tel : +82-42-821-7081 Fax : +82-42-822-9401 w g w w. œw š (SHS) œ w», š w š þ»» z ƒ w j z ƒ» œ. SHS 4-7) w g w ƒ 99.9% w w y ƒ w, š e x š š ( 99.99999% ) g ƒ ƒ w. 2. x x» p Fig. 1 Table 1 ƒƒ ùkü. e w polyethylene bottle ù wì w z 350 rpm 2 yww.» SUS316 w š,» ü œ y» w.» ü œ» œrv in-gas valveƒ š,» w w ü ü ƒ. Fig. 2 x œ ùkü. r y j» w Ni-Cr v p ü ew. w»ü C-type(W-5%Re vs W-26%Re) 93

94 Á xyá» Á y Fig. 1. Schematic diagram of SHS reactor. Table 1. The Properties of Raw Materials Used in This Study Materials Particle size (mesh) Purity (%) SiO 2 <325 99.16 Mg 20~ 325 99.8 Ar gas 99.999 Manufacturer Samchun Chemical (Daejeon, Korea) Daejung Chemical (Siheung, Korea) Chung-ang Gas (Daejeon, Korea) ew DASTC data logger mw þƒ y 10 Hz t d w w. yw ³»(CIP, cold isostatic pressing) w 30 mm, 50-60 mm» x r w š, x y w š w» w x 130~620 MPa y g x. x š»ü w ü œ k w, š ƒ w 1atm w z Ni-Cr v p ( 1 mm, 220 V, 60 A) y g. z 100 mesh w MgO w HCl(con., 18%) 1 e w š- wš 5~10z w z w. x XRD(SIEMENS, Model :D5000) w. w w» w SEM(JEOL, Model:JSM-5410) w š, ICP ww. 3. š 3.1. e Mg ƒ w x š ³ w. SiO 2 +2Mg=Si+2MgO G 298K = 281.442 KJ/mol (1) yw w t ƒ w w š, Mg y w y y k y.» w 2200 K ùkü» w w ƒ. Fig. 3» Fig. 2. Flow chart of experimental procedure. Fig. 3. Concentrations of reaction species with various initial pressure of inert gas in the reactor calculated by THERMO program. w wz

w w š g 95 Fig. 4. X-ray patterns of reaction products varying with Mg molar ratio before leaching (Mg particle size 20/ 60 mesh, compaction pressure 130 MPa); (a) 2.0 mol, (b) 2.2 mol, (c) 2.4 mol, (d) 2.6 mol, and (e) 2.7 mol.» w» y sx,, ü w w v THERMO w w. w»ü y ƒ ƒw g ƒw ƒ 2» š wš, Mg, SiO, Mg 2 SiO 4 w ƒ Zero ƒ¾. Fig. 4 1 w Mg j» 20/60 mesh wš, x 130 MPa š wš, Mg y g e X-ray z ùkü. Mg ƒ ƒw SiO 2 peakƒ š, Mg 2 Si ƒ w, 2.6 SiO 2 peakƒ. Mg ƒ ƒw Mg SiO 2 O 2 w MgO wš, w û Si Mg Mg 2 Siƒ š d. Mg ƒ ƒw ƒ s ù Mg»yƒ š, x vƒ q w Mg SiO 2 kƒ w š SiO 2 w š. ƒƒ z x yw (Mg 2.0 mol) vƒ x w j» q, yw Mg ƒ x 20~25% vq. Fig. 5. Effects of the compaction pressure and Mg particle size on the relative intensity (Mg particle size 20/60 mesh, 140/200 mesh, Mg molar ratio 2.0 mol). 3.2. e Mg j» w Fig. 5 Si SiO 2 XRD e Mg j» x w ùkü. w Mg j» 20/60 mesh 140/200 mesh w e x w r. x ƒ j, x ƒ ƒw e w ƒ š, w ù š. 20/60 mesh w 620 MPa ƒ x w, 140/200 mesh w x ƒ g w w. Mg ƒ j x»œ j» ƒ j, ƒ w û x e yƒ x w w. Fig. 6 j» X-ray z ù kü j»ƒ j SiO 2 vjƒ ƒ w. ƒ f w w y ù SiO 2 ƒ û š. 3.3. e e w š» z MgO w» w e ww. Fig. 7 e j» Si z e e w ùkü. e w» w (con., 18%), 44«2y(2007)

96 Á xyá» Á y Fig. 6. X-ray diffraction of the product varying with Mg particle size after leaching (Mg molar ratio 2.0 mol, compaction pressure 130 MPa); (a) 20/60 mesh, (b) 60/ 100 mesh, (c) 100/140 mesh, (d) 140/200 mesh, and (e) 200/325 mesh. Fig. 8. Effects of the stirring speed and leaching time on the recovery of the final product (Particle size 325 mesh, temperature 70 o C, HCl conc. 18%). Fig. 9. X-ray diffraction patterns of the product varying with pulp density (Stirring speed 480 rpm, leaching time 3 h, temperature 70 o C); (a) 3.8%, (b) 3.2%, and (c) 2.8%. Fig. 7. Effects of the leaching temperature and Mg particle size on the recovery of the final product (Stirring speed 480 rpm, HCl conc. 18%, time 3 h, pulp density 3.2%). 20 g, 480 rpm, e 3 š w š e j» x ww, w e ƒ ƒw Si z ƒw ƒ 70 o C 100% e š, w Mg j» w» w w x ww Mg j»ƒ ƒw Si z ƒw ƒ 200/325 mesh 94% še w. Fig. 8 w l e w ùkü. e ƒw Si z ƒw š, 3 e w 200 rpm 100% e. Fig. 9 ¾ e e z e š- w ùkü X-ray. x 3.2% w y. w e vƒ k y w e w w š ƒ. Fig. 10 š w w wz

w w š g 97 Fig. 11. SEM photographs of final product synthesized at optimum condition. Fig. 10. X-ray patterns of the product before and after leaching (Stirring speed 480 rpm, particle size 325 mesh, temperature 70 o C, time 3 h, HCl conc. 18%, pulp density 3.2%); (a) before leaching and (b) after leaching. e z w. e x e 70 o C, e 3, 480 rpm, j» 325 mesh, 3.2% ww. w» w w» w š ƒ w e ww. e ww z z w, 100 o C» w. w e z MgO š, w ICP w 99.9% Si ùkü. w» SEM Fig. 11 ùkü, 2~3 µm w x. 4. š w SiO 2 /Mg Mg, Mg j»,, x, e x ww z. 1. š Mg j»ƒ, x ƒw. Mg j»ƒ 20/60 mesh Mg 2.6, x 620 MPa. 140/200 mesh 2.0. 2. e j»,,, ƒw e z ƒw, e 70 o C, j» 325 mesh w, 480 rpm, e 3, 3.2%. 3. š e mw, g w 99.9% 2~3 µm w x. REFERENCES 1. J. H. Lee, W. K. Choo, and K. S. Go, The Preparation of High-Purity Silicon by Hydrogen Reduction of Trichlorosilane, J. Kor. Inst. Met & Mater., 14 [3] 288-95 (1976). 2. D. Kata, J. Lis, and R. Pampuch, Combustion Synthesis of Multiphase Powders in the Si---C---N System, Solid State Ionics, 101-103 Part 1, November 65-70 (1997). 3. B. W. Jong, Formation of Silicon Carbide from Silica Residues and Carbon, Bull. Am. Ceram. Soc., 58 [8] 788-89 (1979). 4. C. A. Slack, Nonmetallic Crystal with High Thermal Conductivity, J. Phys. Chem. Solid, 34 321-35 (1973). 5. A. G. Merzhanov, Combustion Processes That Synthesize Materials, J. Mater. Processing Tech., 56 [1-4]G 222-41 (1996). 6. J. Kiser and R. M. Spriggs, Soviet SHS Technology: A Potential U. S. Advantage in Ceramics, Ceram. Bull., 68 [6] 1165-67 (1989). 44«2y(2007)