KAERI/RR-2237/2001 : 원자력재료기술개발 : 기능성재료

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동범 민
6 years ago
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216 Progress in Wire Technology YBCO wire micron thick YBCO on Ni substrate with textured YSZ buffer layer yields 1,200,000 A/cm 2 at 75 K and 0 T and 200,000 A/cm 2 at 75 K and 1 T (LANL) BSCCO wire - rolled, multifilamentary Bi-2223 wire yields 44,000 A/cm 2 at 77 K and 0 T (ASC/WDG) - short, pressed Bi-2223 wire yields 74,000 A/cm 2 at 77 K and 0 T (ANL) TBCCO wire - electrodeposited wire made from Tl-1223 on Ag foil yields Jc of 68,000 A/cm 2 at 77 K and 0 T (NREL) - spray pyrolyzed Tl-1223 on ceramic yields Jc of 325,000 A/cm 2 at 77 K and 0 T (GE/ORNL) Progress in Systems Technology Long-length wire meters, Bi-2223/Ag powder-in-tube wire manufactured by ASC with Jc = 12,500 A/cm 2 (WDG) meters, Bi-2223/Ag powder-in-tube wire manufactured by ASC with Jc = 12,000 A/cm 2 (ANL) Coils - ASC: Bi-2223 coils at 4.2 K, B = 3.3 T / at 30 K, B = 2.6 T / at 77 K, B = 0.6 T - IGC: Bi-2223 coils at 4.2 K, B = 3.2 T / at 27 K, B = 2.2 T / at 77 K, B = 0.38 T - Oxford: Bi-2212 coils at 4.2 K, B = 1.1 T / at 15 K, B = 1.0 T

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219 S1 S2 S3 S4 C O Si S S1 S2 S3 S4 C O Si S Atomic % Atomic % Surface Center Distance (µm) Surface Center Distance (µm)

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221 PACKING density diameter length SHEATH strength chemical compatibility processability conductivity POWDER surface area size distribution impurities, additives stoichiometry FORMING % area reduction method of cold work speed of operation lubricant POST PROCESSING tape strain state current transfer length sample damage Ic criterion SINTERING temperature heat/cool rates atmosphere pressure time Fig. 2. Complexity surrounding Jc improvements.

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223 0 Weight change (mg/cm 2 ) RBSC (48vol% SiC filler) RBSC (60vol% SiC filler) 360 o C, pure water Corrosion for 7 days -8 RBSC (35vol% SiC filler) Fig Weight change of RBSCs after corrosion test in pure water at 360 for 7 days. β-sic (A) RBSC (48 vol% SiC filler) Before corrosion test CPS (a.u.) Si α-sic α-sic β-sic α-sic Si α-sic Si β-sic α-sic β-sic α-sic β-sic θ (degree) β-sic RBSC (48 vol% SiC filler) Corrosion test, pure water, 400 o C, 7 days (B) CPS (a.u.) Si α-sic α-sic β-sic α-sic α-sic Si β-sic α-sic β-sic α-sic β-sic θ (degree) Fig XRD results of RBSC before (A) and after (B) corrosion test in pure water at 360 for 7 days.

224 (A) (B) (C) (D) (E) Fig Cross-sectional ((A), (C)) and surface ((B), (D)) microstructures of RBSC (48 vol% SiC filler) after corrosion test in pure water at 360 ((A), (B)) and in 35 ppm LiOH solution at 360 ((C), (D)) for 7 days. Surface microstructure of RBSC before corrosion test is also included (E).

225 Weight loss (mg/cm 2 ) RBSC (35 vol% SiC filler) RBSC (48 vol% SiC filler) RBSC (60 vol% SiC filler) 0 Specimen type Fig Weight loss of RBSCs after corrosion test in 35 ppm LiOH solution at 360 for 7 days. 4.0 Weight loss (mg/cm 2 ) CVD-SiC Sintered-SiC Time (days) Fig Weight loss of sintered and CVD SiC after corrosion test at 360 C in pure water.

226 (A) (B) (C) (D) Fig Microstructures of as-received (a) and corroded sintered SiC specimens after corrosion at 360 for 1 (b), 5 (c), and 7 (d) days in pure water. Fig Microstructures of as-received (a) and corroded CVD SiC specimens after corrosion at 360 for 3 (b), 7 (c), and 10 (d) days in pure water.

227 Weight change(mg/cm 2 ) Y 6Y2A 360 o C, pure water Corrosion for 7 days 4Y3A (A) 4Y1S 0-5 Weight change(mg/cm 2 ) (B) 8Y 6Y2A 4Y3A 360 o C, water + 70 ppm LiOH Corrosion for 7 days 4Y1S Fig Weight change of Si 3 N 4 specimens after corrosion test in pure water (A) and in 70 ppm LiOH solution (B) at 360 for 7 days.

228 pure water LiOH 35ppm Weight loss (mg/mm 2 ) Time (day) Fig Weight loss as a function of corrosion time at 300 C pure water and LiOH solution pure water LiOH 35ppm Flexural strength(mpa) Time (day) Fig Variation of 4-pt flexural strength as a function of corrosion time at 300 C pure water and LiOH solution.

229 (a) (b) (c) (d) (e) Fig SEM microstructures of Si 3 N 4 ceramics before corrosion test (a) and after corrosion at 300 C for 12 h in pure water ((b), (c)) and LiOH solution ((d), (e)).

230 specimen Rotating axis Autoclave wall Loading by MG coupler Rotating disk Wear-face

231 Specific wear rate (mm2/n) 1E-5 96% Al2O3 99.7% Al2O3 1E-6 1E-7 1E-8 1E-9 1E Temperature (C) % Al2O3 99.7% Al2O3 Friction coefficient Temperature (c)

232 (a) (b) (c) % SEM ( 50 micro- m) (a) (30oC), (b) 100oC, (c) 200oC (a) (b) (c) % SEM ( 50microm) (a) (30oC), (b) 100oC, (c) 200oC

233 (a) (b) (c) SN300 Si3N4 SEM ( 50 micro-m) (a) (30oC), (b) 100oC, (c) 200oC 1E-4 Specific wear rate (mm2/n) 1E-5 1E-6 1E-7 1E-8 1E-9 Ssanyong SN Temperature (C) Si3N4

1-3-1. 99.7 wt% EDX 2.0 1.8 Si composition (wt%) 1.6 1.4 1.2 1.0 0.8 0.

234 wt% EDX Si composition (wt%) % Al2O3 96% Al2O Time (h) oC Si

235 Flexural strength (kgf/mm^2) AR G B GB Kind of specimens Mean ,, 100 oc, 100 oc

236 fluence cell V/Vmacro

237 (b) (a) (a) 300 gf loading, (b) 500 gf loading

238 o o o L i 2 T io 3 F : o n l y g l y c i n e o o o o o o o o o o E : o n ly c itr ic a c id D : U re a < c it. a c id C : U re a = c it. a c id B : U re a > c it. a c id A : o n ly u re a T H E T A Fig XRD patterns of as-synthesized powders with various fuel type and compositions Fig SEM and TEM micrographs of the as-synthesized Li 2 TiO 3 powder with glycine fuel.

239 10 melting DSC (mw/mg) 0 ENDO EXO Temperature ( o C) Fig DSC curve of the glycine in air condition with heating rate of 10 o C/min 10 5 EXO DSC (mw/mg) o C 330 o C o C Temperature ( o C) Fig DSC curve of the glycine-fueled LiNO 3 -TiO(NO 3 ) 2 precursor in air condition

240 Weight loss (mg) TG DTA Thermal difference (uv) Temperature ( o C) -4 Fig Differential Thermal Analysis and Thermogravimetric Analysis patterns for the as-synthesized Li 2 TiO 3 powder (with glycine fuel) CPS fuel-rich (200% of stoi.) fuel-stoichiometric o o fuel-lean (50% of stoi.) o oo o Theta Fig XRD patterns for Li 2 TiO 3 combusted under three glycine/nitrate ratio. (Stoichiometric and rich burn produced crystalline LT only and Fuel-lean produce mainly TiO 2 (open circle: anatase) and LT phase.

L T L T : L i 2 T i O 3 L T (d ) L T L T L T L T L T L T L T (c )

x o o o o o o o o 1 0 2 0 3 0 4 0 5 0 6 0 7 0 2 T H E T A Fig.

XRD patterns of the Li 2 TiO 3 powder prepared by solid-state

for 3h (c) at 700 o C for 3h, and (d) at 1000 o C for 3h Fig.

Microstructure of the Li 2 TiO 3 compact made by solid state

241 L T L T : L i 2 T i O 3 L T (d ) L T L T L T L T L T L T L T (c ) (b ) o x o x : a n a t a s e ( T i O 2 ) : L i 2 C O 3 (a ) x x x x o o o o o o o o T H E T A Fig XRD patterns of the Li 2 TiO 3 powder prepared by solid-state reaction; (a) after oven-drying, (b) after calcination at 550 o C for 3h (c) at 700 o C for 3h, and (d) at 1000 o C for 3h Fig Microstructure of the Li 2 TiO 3 compact made by solid state reaction (a) sintered at 700 o C for 3h, and (b) 1000 o C for 3h. And the Li 2 TiO 3 compact synthesized by combustion reaction (c) sintered at 550 o C for 3h, (d) 700 o C and (e) 1000 o C for 3h, respectively.

(a) after sintered at 550 o C for 3h, and (b) 700 o C for 3h,

Pinn (4h, vacuum, ANL) sol-gel (2h, france) KAERI (2h, combustion)

242 Fig Surface morphology of the Li 2 TiO 3 prepared by combustion reaction (a) after sintered at 550 o C for 3h, and (b) 700 o C for 3h, respectively Relative density (%) J.M.Miller (4h, AECL) F.A. Pinn (4h, vacuum, ANL) sol-gel (2h, france) KAERI (2h, combustion) KAERI (4h, combustion) KAERI (10h, combustion) KAERI (2h, Aldrich Co.) KAERI (4h, Aldrich Co.) Sintering Temperature ( o C) Fig Effects of powder preparation method and sintering temperature on the relative density of sintered Li 2 TiO 3 compacts.

: Cu : CuO : Cu 2 O RELATIVE INTENSITY C B A 20 30 40 50 60 70 80 2 THETA Fig. 2-1-11.

243 : Cu : CuO : Cu 2 O RELATIVE INTENSITY C B A THETA Fig XRD patterns of as-synthesized ODC powders with various fuels ; (A) urea, (B) 1 urea + 1 glycine and (C) 2 urea + 1 glycine. Fig TEM micrographs of Al 2 O 3 -CuO powder prepared by the combustion process and EDS result.

A : as -s ynthes ized before re duc tion B : after s elective reduction RELATIVE INTENSITY : Cu : CuO B A Fig. 2-1-13.

244 A : as -s ynthes ized before re duc tion B : after s elective reduction RELATIVE INTENSITY : Cu : CuO B A Fig XRD patterns of Al 2 O 3 dispersed Cu powder ; (A) before reduction and (B) after reduction THETA (A) (B) (C) Fig Surface flaws of Al 2 O 3 dispersed Cu alloy extruded at (A) 550 o C, (B) 700 o C and (C) 750 o C

245 Fig Transmission electron micrograph (A) of the extruded Al 2 O 3 -Cu using the combustion synthesized powder, the magnified micrograph (B) of the white Particle, and EDS results ; (C) mark C particle in Fig. (A) and (D) mark D Grain in Fig. (A).

246 Tensile strength (Kg/mm 2 ) KAERI (H.E 750 o C, annealing 600 o C/1h) AL-25 (as-hot extruded) AL-15 (as-hot extruded) AL-15 (T.J.Miller, H.E, annealing 600 o C/1h) pure copper Temperature ( o C) Fig Tensile strength of pure copper and ODS Cu Fig Electrical conductivity of pure copper and Al 2 O 3 -dispersed Cu

247 Fig

Microstructure of the Li 2 TiO 3 powders

ultrasonic mist combustion process (with

248 Fig XRD patterns of as-synthesized powders made by ultrasonic mist combustion/pyrolysis process Fig Microstructure of the Li 2 TiO 3 powders made by ultrasonic mist combustion/pyrolysis process (A) ultrasonic mist combustion process (with fuel) and (B) ultrasonic mist pyrolysis process (without fuel), respectively.

Fracture morphology of the Li 2 TiO 3 pellets sintered

249 Fig Thermogravimetric analysis patterns of the Li 2 TiO 3 powders made by ultrasonic mist combustion/pyrolysis process Fig Fracture morphology of the Li 2 TiO 3 pellets sintered at 1000 o C for 2h (A) ultrasonic mist combustion process (with fuel) and (B) ultrasonic mist pyrolysis process (without fuel), respectively.

3500 3000 2500 Intensity 2000 1500 1000 500 0 950 o C 900 o C 850 o C 800 o C 750 o C 700 o

250 Intensity o C 900 o C 850 o C 800 o C 750 o C 700 o C Fig XRD patterns of Al 2 O 3 dispersed Cu powder made by ultrasonic mist combustion process with various reduction temperature Fig Transmission electron micrograph and EDS results of the Al 2 O 3 - Cu powder after reducing process

251 Tensile strength (Kg/mm 2 ) KAERI UMCP Al-15 Al-25 pure copper Temperature ( o C) Fig Tensile strength of pure copper and ODS Cu 60 Electrical conductivity (Meg S/m) KAERI (batch type) AL-15 AL-25 KAERI (UMCP) pure Cu 0 Specimen type Fig Electrical conductivity of pure copper and Al 2 O 3 -dispersed Cu

ultrasonic mist combustion process Fig. 2-1-28.

252 Fig XRD patterns of Cu-Ni alloy powders made by ultrasonic mist combustion process Fig SEM and TEM micrographs of the Cu-Ni alloy powders made by ultrasonic mist combustion process

253 (A) Ni (B) 0.1% Cr 2 O 3 -Ni (C) 0.3% Cr 2 O 3 -Ni (D) 0.5% Cr 2 O 3 -Ni (E) 7.0% Cr 2 O 3 -Ni O O O : Ni * : Cr 2 O 3 CPS * * * * * * (E) (D) (C) (B) (A) THETA Fig X-ray diffraction patterns of the synthesized powders by the metal salt reduction process; (A) Ni, (B) 0.1% Cr 2 O 3 -Ni, (C) 0.3% Cr 2 O 3 -Ni, and (D) 0.5% Cr 2 O 3 -Ni powder, respectively Relative Density (%) o C for 2h 1000 o C for 2h 70 Ni Ni-0.1Cr2O3 Ni-0.3Cr2O3 Ni-0.5Cr2O3 Fig Sintered density of the specimen with sintering temperature.

254 Fig Transmission electron micrograph (A) fo the 0.3% Cr 2 O 3 nickel and EDS results; (B) the nickel grain of (A), and (C) the Cr 2 O 3 dispersed particles of (A).

240 220 900 o C for 2h 1000 o C for 2h 200 180 Hardness

255 o C for 2h 1000 o C for 2h Hardness (kg/mm 2 ) NI Ni-0.1Cr2O3 Ni-0.3Cr2O3 Ni-0.5Cr2O3 Fig Microhardness values of sintered specimen with the Cr 2 O 3 content of Ni. Fig

256 CVD APPARATUS MFC (1) (2) (9) (11) MFC MFC P (5) (3) P (7) (8) (10) P.F (4) (6) SCRUBBER MTS P Ar H2 ICE BATH PUMP (12) EXHAUST Fig Schematic diagram of horizontal CVD reactor Ln Deposition Rate(mg/cm 2 /m in) torr 5torr 10torr 50torr 100torr /T(K) Fig Deposition rate as a function of deposition temperature with various system pressure..

257 o C Linear velocity(cm/s) o C 1250 o C 1300 o C Residual time(s) Total system pressure(torr) Fig Change of linear velocity and residence time as a function of total system pressure o C 1250 o C 1300 o C 10torr 50torr 100torr Fig Microstructural change of SiC deposits with deposition temperature and system pressure.

258 Fig Microstructural map of SiC deposits. MTS Stainless steel chamber Graphite insulation Graphite heating elemen Constant temp. bath Substrate (graphite) Graphite isolation tube Furnace pressure control valve Vac. pump Gas scrubber Filter Fig Schematic diagram of large area CVD reactor.

259 Table Experimental condition for large area CVD. Source : Methyltrichlorosilane (MTS) Diluent & carrier gas : H 2 Deposition temperature : 1200 ~1350 C, 1 h Chamber pressure : 25~50 torr MTS flow rate : 0.5 slm Total flow rate : 3.0 slm H 2 /MTS ratio : 5 Substrate rotation speed : 2~10 rpm Temperature uniformity : < 2 o C 50 Deposition rate (µm/h) Deposition temperature ( o C) Fig Deposition rate as a function of deposition temperature for a graphite substrate with a diameter of 15 cm.

260 Deposition rate Kinetic limited Mass transport limited Thermodynamics limited Temp. Fig Different reaction regimes in a CVD process. G : graphite Indexed : β-sic (220) 1350 o C CPS (a.u.) (111) (311) 1300 o C G (222) G (111) G 1200 o C G θ (degree) Fig XRD patterns of SiC layer deposited at various temperatures.

261 Atomic percent (%) Si C 10 O Etch time (sec) Fig AES result of deposited SiC layer C 1300 C 1350 C Fig SEM microstructures of deposited SiC.

262 4 Average grain size (µ m) (A) horizontal vertical Distance from center (cm) 10 Average grain size (µ m) (B) horizontal ve rtica l Distance from center (cm) Fig Grain size distribution of SiC layer deposited at (A) 1300 C and (B) 1350 C.

263 Deposition thickness (µ m) (A) horizontal vertical Distance from center (cm) Deposition thickness (µm) 90 (B) horizontal vertical Distance from center (cm) Fig Thickness distribution of SiC layer deposited at (A) 1300 C and (B) 1350 C.

1.8 1.6 Relative thickness 1.4 1.2 1.0 0.8 0.6 Avg. t = 165 µm 0.4 0.2 7.5 5.0 2.5 0 2.5 5.0 7.

Thickness distribution of SiC layer when the position of gas inlet nozzle is off-axis from the center of the

264 Relative thickness Avg. t = 165 µm Distance from center (cm) Fig Thickness distribution of SiC layer when the position of gas inlet nozzle is off-axis from the center of the substrate. (a) (b) Fig Surface and cross-sectional microstructures of the center region of SiC layer when the position of gas inlet nozzle is off-axis from the center of the substrate.

265 (a) (b) Fig Expected gas flow patterns when the position of gas inlet nozzle is off-axis (A) or on-axis (B) from the center of the graphite substrate Relative thickness Avg. t = 76 µm Position on substrate Fig Thickness distribution of SiC layer when the position of gas inlet nozzle is on-axis from the center of the substrate. Deposited at 1350 for 1 h.

1.4 Relative thickness 1.2 1.0 0.8 0.6 0.4 Avg. t = 25.7 µm 0.2 7.5 5.0 2.5 0 2.5 5.0 7.5 Distance from center (cm) Fig. 2-2-18.

266 1.4 Relative thickness Avg. t = 25.7 µm Distance from center (cm) Fig Thickness distribution of SiC layer when the position of gas inlet nozzle is on-axis from the center of the substrate. Deposited at 1300 for 1 h. Fig Macroscopic view of SiC-deposited graphite with a diameter of 25 cm.

1.4 Relative thickness 1.2 1.0 0.8 0.6 0.4 Avg. t = 93.8 µm 0.2 12.5 10.0 7.5 5.0 2.5 0 2.

Thickness distribution of SiC layer deposited on 25 cm graphite substrate at 1300 for 4 h.

267 1.4 Relative thickness Avg. t = 93.8 µm Distance from center (cm) Fig Thickness distribution of SiC layer deposited on 25 cm graphite substrate at 1300 for 4 h. Fig Cross-sectional microstructures of rim (A) and center (B) region of SiC layer deposited on 25 cm graphite substrate.

268 MTS:C 2 H 2 = 100:100 SiC Graphite Equilibrium yield (mole) Temperature ( o C) Fig Calculated relation between deposition temperature and yield of PyC and SiC. 100 C/(C + SiC) (vol%) log(c 2 H 2 /CH 3 SiCl 3 ) Fig Calculated relation between the input gas ratio and C/(C+SiC) at 1300, 10torr.

SiC C/SiC C/C Fig. 2-2-24. Polished cross-sectional morphology of C/SiC compositionally graded layers (back scattered electron image).

269 SiC C/SiC C/C Fig Polished cross-sectional morphology of C/SiC compositionally graded layers (back scattered electron image). 30 Vickers hardness (GPa) Theoretical Measured log(c 2 H 2 /CH 3 SiCl 3 ) Fig Comparison between calculated (line) and measured (symbols) hardness of C/SiC layers.

270 Carbon β-sic PyC MTS20 MTS50 MTS70 MTS80 MTS θ Fig XRD patterns of the C/SiC layers by changing the input gas ratio. 100 C/(C + SiC) (vol%) Theoretical composition Measured composition log(c 2 H 2 /CH 3 SiCl 3 ) Fig Comparison between calculated (line) and measured (points) composition of C/SiC layers deposited at 1300, 10torr

Fig. 2-2-28. X-ray mapping of Si for C/SiC compositionally graded layers. 1.75 Crack length/unit area(cm/cm 2 ) 1.63 1.50 1.38 1.25 1.

271 Fig X-ray mapping of Si for C/SiC compositionally graded layers Crack length/unit area(cm/cm 2 ) non-fgm 2 step FGM 5 step FGM 10 step FGM Fig Effect of FGM interlayer on the cracking behavior of SiC-coated C-C composites.

272 60 50 Hardness (GPa) Faceted microstructure Displacement (nm) 50 Hardness (GPa) Round-top microstructure Displacement (nm) Fig Hardness of CVD SiC with different microstructure measured by nanoindentation.

50 40 Hardness (GPa) 30 20 10 d = 70 µm 0 d = 50 µm 0 2 4 6 8 10 12 Indentation load (N) Fig. 2-2-31.

273 50 40 Hardness (GPa) d = 70 µm 0 d = 50 µm Indentation load (N) Fig Hardness as a function of indentation load in microhardness test of SiC/graphite at coating thickness of 70 µm and 50 µm, respectively. Fig Surface views of microhardness contact damage in SiC/graphite structure with coating thickness, d = 50 µm: at indentation load (a) P = 2 N showing radial cracks and (b) P = 3 N showing ring crack.

274 6.0 Toughness (MPam 1/2 ) Coating thickness (µm) Fig Effects of coating thickness on toughness of SiC/graphite at indentation load of 2 N.

275 (a) (b) Section Grinding 300 µm Fig Micrographs of surface damage in SiC/graphite with different coating thickness; (a) d = 70 µm and (b) d = 50 µm after Hertzian indentation at load P = 50 N with WC ball r = 3.18 mm.

276 150 Indentation Stress, Po (kg f /mm 2 ) E = 4900 kg f /mm 2 E = 694 kg f /mm 2 55 µ m coated 70 µ m coated 110 µm coated 140 µm coated Indenatation Strain, a/r Fig Indentation stress-strain curves of SiC coated graphites with coating thicknes µm coated 70 µm coated 110 µm coated 140 µm coated Hardness (kg f /mm 2 ) Applied Load (g f ) Fig Hardness of SiC coated graphite with coating thickness.

277 Fig Schematics of crack propagation and stress-strain behavior in CFCCs. Fig Schematic diagram of the ceramic fiber/matrix interface in CFCCs. (a) typical result with uncontrolled interface and (b) that with the ideal interfacial system.

278 Fig Reactant and product gas concentrations as a function of axial position down a cylindrical pore: ( ) concentration under diffusion rate limiting conditions; ( ) concentration under chemical kinetic rate limiting conditions. Fig Geometrical features of the straight cylindrical model pore.

279 Fig Calculated thickness profiles of SiC based ceramics in the CH 3 SiCl 3 -H 2 system for various temperature, (b) total pressure, (c) aspect ratios L/ o with constant diameter o, and (d) diameters with constant L/ o.

280 Fig The five classes of CVI techniques.

281 Fig CVD diagram at 1atm (a) SiH4/CH4/H2, (b) SiCl4/CCl4/H2, (c) CH3SiCl3/H2, (d) (CH3)2SiCl2/H2

282 Fig Schematics of the silicon carbide whisker growth mechanisms. (a) vapor-solid growth mechanism, (b) two stage growth mechanism, (c) vapor-liquid-solid growth mechanism.

283 reactor reactor control console gas control console Fig Photograph of FCVI system. Fig Schematic diagram of reactor core.

284 Silicon Carbide fabric 2D Plain Woven Nicalon Interlayer Coating 950 o C, 5 torr, CH 4, for 4 hr Preform Matrix Filling 1000 o C, 100 torr, MTS/H 2, for 5 hr Matrix Filling 950~1100 o C, 100 torr, MTS/H 2, for 24 h XRD, SEM, Density, Bending test Fig Flow diagram of SiC/SiC composite fabrication

285 (a) (b) (c) Fig SEM photography of C/SiC composites fabricated with infiltration temperature using H 2 dilute gas ; (a) 1100, (b) 1200, (c) 1300.

286 (a) (b) (c) Fig SEM photography of C/SiC composites fabricated with infiltration temperature using N 2 dilute gas ; (a) 1100, (b) 1200, (c) 1300.

287 (a) (b) Fig SEM photography of C/SiC composites fabricated at 1100 ; (a) H 2 (2hr)-N 2 (6hr) (b) H 2 (2hr)-N 2 (2hr)-H 2 (2hr)-N 2 (2hr).

288 α=15 α=15 α=15 α=20 α=20 α=20 α=25 α=25 α=25 Fig SEM images of SiC f /SiC composites with reaction temperature and input gas ratio.

289 gas flow inlet outlet µ hr α = 20 α = 30 α = 40-4hr α = 20 α = 30 α = 40 µ 2 1-2hr α = 20 α = 30 α = 40-4hr α = 20 α = 30 α = inlet outlet (a) inlet outlet (b) Fig The comparison of (a) whisker length (b) whisker diameter with variation of input gas ratio at 1100 µ hr α = 20 α = 25 α = 30 α = 40-4hr α = 15 α = 20 α = 25 µ 2 1-2hr α = 20 α = 25 α = 30 α = 40-4hr α = 15 α = 20 α = inlet outlet (a) inlet outlet (b) Fig the comparison of (a) whisker length (b) whisker diameter with variation of input gas ratio at 1150

290 Fig SEM images of SiC / SiC composites which were prepared using hydrogen Dilute gas at 1100, = 20

291 Fig SEM images of SiC / SiC composites which were prepared using hydrogen dilute gas at 1150, = 20

292 (A) (B) Fig SEM images of SiC/SiC composites which were prepared by (A) two-step process and (B) four-step process.

293 Fig Microstructures of SiC f /SiC composites prepared by (a) 5h + 24h matrix filling and (b) 5 h whiskering +24 h matrix filling.

294 Density (g/cm 3 ) Temp. ( o C) Density (g/cm 3 ) torr 100 torr Pressure(torr) whisker- filling Fig Bulk density of SiC f /SiC composites after the SiC matrix filling as a function of (a) reaction temperature and (b) reaction pressure. Load(kN) Whiskher-filling 1000 O C 950 O C 1000 O C 1050 O C whisker-filling O C 950 O C Crosshead Displacement(mm) Fig Comparison of three-point flexure curves of SiC f /SiC with varied matrix filling process.

250 200 Flexural Strength (MPa) 150 100 50 0 950 1000 Temperature ( o C) 1050 250 Flextural Strength (MPa) 200 150 100 50 0 50 torr 100 torr whisker-filling Fig. 2-3-24.

295 Flexural Strength (MPa) Temperature ( o C) Flextural Strength (MPa) torr 100 torr whisker-filling Fig Flexural strength of SiC f /SiC composites after the SiC matrix filling as a function of (a) reaction temperature and (b) reaction pressure. Fig Tubular SiC f /SiC composite and supporter for the preparation of it.

296 Fig Microstructures of SiCf/SiC composites infiltrated (a) without the whisker growing at 1000 o C for 5 h and with the whisker growing for (b) 2 h, (c) 4 h and (d) 6 h at 1100 o C.

297 Fig Cross section of SiCf/SiC composites infiltrated (a)without the whisker growing at 1000 o C for 5 h and (b)with the whisker growing at 1100 o C for 4 h.

298 Fig Microstructures of SiC f /SiC composites prepared by (a) 5 h + 5 h matrix filling and (b) 6 h whiskering + 5 h matrix filling. (c) and (d) are the cross sections of (a) and (b), respectively.

299 Fig A schematic diagram of the whiskering process.

300

301

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303 50 45 Nicalon (as-recieved) Nicalon (1800 o C) Frequency (number) Frequency (number) Diameter (µm) Diameter (µ m) Nicalon (1900 o C) 40 Frequency (number) Diameter (µm) Nicalon (2000 o C) 45 Nicalon (2100 o C) Frequency (number) Frequency (number) Diameter (µ m) Diameter (µm)

304 Diameter (µm) As-recieved Heating temperature ( o C)

305 Mixing raw materials (Bi 2 O 3, PbO, SrCO 3, CaCO 3, CuO) Calcination in air Calcination in vacuum 700ºC, 12 h 800ºC, 8 h (X2) 720ºC, 5 h, 3 torr O 2 Degassing 760º~800ºC, 8 h (X2) 3 torr flowing O 2 PIT processing Heat treatment Analysis 840ºC, ~200 h, air Fig Experimental procedure Ca 2 PbO 4 CuO AEC (B) (A) (C) CPS (a.u.) (B) [0211] (A) θ (degree) Fig XRD patterns of the precursor powders calcined in (A) air and reduced oxygen pressure at (B) 760 C and (C) 780 C.

at 760 C 18 16 Critical current density (ka/cm 2 ) 14 12 10 8 6 4 2 0 Air calcine Vacuum calcine 50

306 (A) (B) Fig SEM micrographs of the precursor powders calcined (a) in air at 800 C and (B) in low oxygen pressure at 760 C Critical current density (ka/cm 2 ) Air calcine Vacuum calcine Cumulative annealing time (h) Fig Critical current densities of the tapes fabricated by the air-calcined and the vacuum-calcined powders. The tapes were sintered at 840 C.

XRD patterns of the tapes fabricated by (A) the

Backscattered electron micrographs of the tapes

307 CPS (a.u.) (B) (A) θ (degree) Fig XRD patterns of the tapes fabricated by (A) the air-calcined and (B) the vacuum-calcined powders after sintering at 840 C for 50 h. (A) (B) (C) (D) Fig Backscattered electron micrographs of the tapes fabricated by the air-calcined ((A), (B)) and the vacuum-calcined ((C), (D)) powders. (A) and (C): sintered at 840 C for 50 h; (B): 200 h; (D): 150 h.

308 Mixing raw materials 24 h in alcohol Calcination & Grinding 700ºC, 12 h 800ºC, 8 h (X2) Addition of 2223 particles Ball milling Mixing 8 h in alcohol 24 h in alcohol Drying & Degassing 720ºC, 5 h, 3 torr O 2 PIT processing Air-quenching Heat treatment 840ºC, ~200 h, air Analysis Fig Experimental procedure Ca 2 PbO 4 (C) CPS (a.u.) (B) (A) θ (degree) Fig X-ray diffraction patterns of the precursor powders containing (A) 0, (B) 1, and (C) 5 wt% 2223 seed particles.

309 Critical current density (ka/cm 2 ) no seed 1 wt% seed 3 wt% seed 5 wt% seed 10 wt% seed Annealing time (hrs.) Fig Critical current density of the tapes containing various amounts of 2223 seed particles. The tapes were sintered up to 100 h without intermediate mechanical deformation CPS (a.u.) (B) (A) θ (degree) Fig X-ray diffraction patterns of the tapes containing (A) 0 and (B) 1 wt% 2223 seed particles after sintering at 840 C for 50 h.

16 24 Critical current density (ka/cm 2 ) 14 12 10 8 6 4 2 0 (A) no seed 1 wt% seed 3 wt%

Cumulative annealing time (hrs.) 50 100 150 200 Cumulative annealing time (hrs.) Fig.

Critical current density of the tapes containing various amounts of 2223 seed particles.

310 16 24 Critical current density (ka/cm 2 ) (A) no seed 1 wt% seed 3 wt% seed 5 wt% seed Critical current density (ka/cm 2 ) (B) Cumulative annealing time (hrs.) Cumulative annealing time (hrs.) Fig Critical current density of the tapes containing various amounts of 2223 seed particles. The tapes were sintered three times at 840 C for a total time of 200 h with two intermediate pressing steps. The soaking period in the first sintering step was controlled to (A) 50 h or (B) 35 h. (A) (B) (C) (D) Fig Microstructures of the tapes containing (A) no seed, (B) 1, (C) 5, and (D) 10 wt% seed particles after sintering at 840 C for 200 h.

311 Volume fraction of 2223 phase (%) no seed 1 wt% seed 5 wt% seed Annealing time (hrs.) Fig Transformed fraction of 2223 phase as a function of annealing time for the tapes containing 0, 1, and 5 wt% seed particles. 1 0 no seed 1 wt% seed 5 wt% seed ln [-ln(1-f)] ln (t) Fig Kinetics of 2223 phase formation for the tapes containing 0, 1, and 5 wt% seed particles.

312 (A) (B) Fig Microstructures of (A) the spray dried powder and (B) the calcined powder.. Fig TG/DTA curve of the spray dried powder.

313 14 12 Critical current (A) spray dried powder solid-state reacted powder Cumulative annealing time (h) Fig Critical current of the tapes fabricated by the spray dried powder and solid-state reacted powder. Annealing time: 150h total Critical current (A) Annealing temperature ( o C) Fig Critical current of the 37 multifilamentary tapes sintered at different temeratures.

314 (A) As-rolled (B) Final tape Fig Transverse and longitudinal microstructures of the 37 multifilamentary tapes before and after sintering wt% seed 10 Ic (A) Tape Number Fig Summary of critical current of the 25m long 37 multifilamentary tapes.

315 Fig Photographs of the 100m long multifilamentary tapes.

316 Ic/Ico H : parallel to tape surface H : perpendicular to tape surface Back-up field (T) PIT Bi-2223 (77.3 K) double pancake

317 Voltage drop (V) total magnet nd DPC mid DPC Transport current (A) K ( 160 m )

318 z- directional field intensity (T) A : Fz max = (T) A : Fzmax = (T) location along center axis (cm) z z

319 3-3-1.

320 ( 25 K, 45K, 80K,85k, zero field cooling, 5 mm )

321 3-3-3.

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323 ring type (a) (b) (a) Halbach array, (b) Halbach (2 )

324 ( ) RPM Time (sec)

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14.fm 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