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Carbon Science Vol. 7, No. 4 December 2006 pp. 271-276 Effect of Heating Rate and Pressure on Pore Growth of Porous Carbon Materials Kwang Youn Cho, Kyong Ja Kim and Doh Hyung Riu Division of Nano Materials Application, KICET, Seoul 153-851, Korea e-mail: kycho@kicet.re.kr (Received September 18, 2006; Accepted December 11, 2006) Abstract Porous carbon materials were prepared with a thermal treatment of coal tar pitch at 550 in the Ar gas. Growth, merger, and distribution of pore were characterized with scanning electron microscopy as variation ascending temperature gradient and chamber pressure. After graphitizing at the 2600 (1 hr.), walls and connecting parts between pores were investigated with X-ray diffraction patterns. Wall thickness and pore size decreases as increasing ascending temperature gradient, and pore size becomes homogeneous. Graphite quality and thermal conductivity become higher due to the enhanced orientation of walls and connecting parts between pores. Keywords : Pore, Growth, Pressure, Heating Rate, Thermal Conductivity 1. ˆ q o r r s c p p q p d a, b p p o p v p p p v p. ˆ q p r s n lr m m l m s q r q p. ˆ o p p rp p p s v p p p l lr p. p lr l q n r l rn l pl ep kv p. c p p lr p 2D, 3D l p l p p [1]. rp c p p lr ~p l l ~ ƒv o l p p e lr. ˆ q o p o o l 1200 o C p ˆ m 2500 o C p p l l rp r s. p rl o p r r p të p ˆ q rs. r r p p 300 o C p l eq l 400~500 o Cl vtrp pl. 500 o C p l d r p l p ~ l p [2]. p rl dm m k srl p s ˆ q p s sr p, dm p ~ n v kp ˆ l p p ~l p k p l p dk p k p ~ l pe p s [3]. dm m k p m ˆ sr pp k l p p eˆ. p 3 orp l s p. p rs ˆ q k, 3 orp l p o~p p qo el rp. p svp ˆ o p p lr k l q ns p seˆ p rp qp [4]. ˆ q p Poco Graphite, Locheed Martin Energy Co., Allied-Signal Inc.m p l l q n e pp r n v p. r l ƒ sm o svp pl ˆ o e ~ p q f p p. ˆ om ˆ q rëlr p p ˆ l pn l p., r rp p rs ˆ o q l ˆ p interlaminar s l l r p p p l n p ˆ p r. ˆ q rs ˆ q o p r} s l k svp. l l rs ˆ n l k o l 550 o C l } l ˆ q rs m. l} e dm m k p l q p m. q p scanning electron microscopy q, ~, l m ˆ q 2600 o C 1e l XRD p ee l l, l p l ˆ m.

272 K. Y. Cho et al. / Carbon Science Vol. 7, No. 4 (2006) 271-276 2. œ k o kr~ (t)p ˆ e p ˆ n m. ˆ 100gp k p l l kn l qp v v d tpp 3 v d tp l 300~800 psi k m. p r k p ov 5 o C/min 500 o C v dm l 30 ov l m. rs ˆ q e p l l qp v Ar dtpp 3 Ar o l 2600 o C v 10 o C/min dmeˆ 1e k ov m [5, 6]. rs ˆ qp r w q rn (AT201, METTLER, Switzerland)m v lƒ d e p m ~rp l tp r m. Gas Pycnometer(Accupyc 1330) n l v tp r t m. e p k rn e p 10 10 20 mm( p)p p e p rq e (Model 4202, Instron JAPAN) 500 kg load cell, cross speed 0.5 mm/minp s p Ž tp, k p (1)el m. σ c = ----- P bd σ c : Compressive strength P : Fracture load b : length(h) d : length(v) dm m k p l rs ˆ qp,, s t rq (SEM, AKASHI, WB-6)p m. 2600 Cl o 1e k l e l Cu ˆ p X- r l l r ˆ t (002) l p q (C 0 /2)m c l rp r m. q Bragg's lawp (2) p ep pn mp rp Scherrer equation (3)p pn l r m [7]. (1) L c : Average stack height of crystalline k : Correction factor (about 1) B : Width of line at half intensity maximum ˆ qp k l p lr r NETZCH LFA427 pn l KS L 1604l p l ln l pp l (4)m p e p lr r m. λ=α*cp*ρ λ : Thermal conductivity α : Thermal diffusivity Cp : Specific heat capacity ρ : Density 3. y w Fig. 1, 2 dm srl p ˆ qp p, p p. dm v p, p v rp qkv r q kr. p dm v o p 500 o C v l l p p q, ~ p t p ˆl pl p ˆ v, qp p ˆ p. Fig. 3p dm srl p rs ˆ q p rq vp. dm ~ v v l r rp p q p kk. p p t pl p qld (4) ( ) = ------------- λ 2sinθ d 002 (2) d : Interlayer spacing θ : Bragg's angle λ : Wavelength of Cu Kα X-ray (1.5406 Å) L c = -------------- kλ Bcosθ (3) Fig. 1. Pore diameter of porous carbon materials as a function of heating rate.

Effect of Heating Rate and Pressure on Pore Growth of Porous Carbon Materials 273 Fig. 2. Ligaments width of porous carbon materials as a function of heating rate. v k rpp p. dm 2 o C/min rs e p p m p rp o p p t p ~ e p v pl p ov p ƒr. Fig. 4 p l} dm l p rs ˆ qp o l e p [1, 2]. rp 3000 o Cl p rl 60%p p. pl 400~500 o C l p. p l p eq l l o p l 350 o C p ~- qp pl p n eq. p t pp p ov eq. pp v lo l p t p ~ p p p t pp p r rp p p qkv eq. p p p t dkp t t l p p p qn l p qkr p l v eq. dm p p p pl l p l r svp. d m p q- ~ kp ˆl p lr qp p p svp. v, dm q kp s v 3 orp l (Foam) ˆp ˆ q. ƒ w Fig. 3. SEM of porous carbon materials as a function of heating rate. Fig. 5, 6p k l ˆ qp, p. k p v p qkr kkr. k p v m p qkr. p l p Fig. 4. Foaming mechanism as a function of heating rate.

274 K. Y. Cho et al. / Carbon Science Vol. 7, No. 4 (2006) 271-276 Fig. 5. Pore diameter of porous carbon materials as a function of pressure. Fig. 6. Ligaments depth of porous carbon materials as function of pressure. p n p k l p po ~ ql l np p r rp p qkr p p r. Fig. 7 k p l rs ˆ qp rq vp. r rp k p q p p pl qp k l qp p q l pl. p k p v p n p l n k l p l l p d kp d l p p q v m, p ~ l l p q p r p Ž. n k 500 psi rs ˆ qp vl qp p q ~p rp p. k l v svp q r p l ˆ om p p q p p. p n k dkp p p p Fig. 7. SEM of porous carbon materials as a function of pressure. l l vt q r s p Ž. p l s rp p p l n lr, r p ˆ. Fig. 8, 9p ˆ q ˆ m l p XRDq p. k l l l r r n m. ˆ XRDl p p l v kkp l XRDq l 002 p l ƒr t p p n qkr. p d (002) p l(3.354 nm)l ov rp (Lc) ƒr v p, r rp k l l l r l d m. Fig. 10, 11 l ˆ qp d(002), l, l r p ˆ l. k l l d(002)p 3.3608 nm qkr l 92%, lr 57.5 W/mK p ˆ l. p 300~500 o C l lo p, el l p dkp p

Effect of Heating Rate and Pressure on Pore Growth of Porous Carbon Materials 275 Fig. 8. XRD of porous carbon materials as a function of pressure after carbonization. Fig. 11. Bulk thermal conductivity and specific thermal conductivity of porous carbon materials as a function pressure. l p p p t l p dk n l v k p p l l vt l p v p. Fig. 9. XRD of porous carbon materials as a function of pressure after graphitization. Fig. 10. d(002), %Graphitization of porous carbon materials as function of pressure. eq p kl p p lo p l r p ~, qp l ov. p p n p p np k l q v ˆp p k p. p m d l t 4. dm l p, p v rp qkv r qkr. dm l p m p rp o. p dm v o p 500 o C v l l p p q, ~ p t p ˆl pl p ˆ v, qp p ˆ p dm p t p ~ e p v pl p ov p ƒr. k p q p p pl q p k l qp p q l pl. n p k p rp qp n qp p q ~p rp p. k p v svp q r p l p q p p. p n k dkp p p p l l vt q r s p Ž. p rs ˆ q d(002)p 3.3608 nm q l 92%, lr 57.5 W/ mk p ˆ n l q p p p. References [1] Druma, A. M.; Alam, M. K.; Druma, C. International Jour-

276 K. Y. Cho et al. / Carbon Science Vol. 7, No. 4 (2006) 271-276 nal of Thermal Sciences 2004, 43, 689. [2] Calvo, M.; García, R.; Arenillas, A.; Suárez, I.; Moinelo, S. R. Fuel 2005, 84, 2184. [3] Beechem, T.; Lafdi, K.; Elgafy, A. Carbon 2005, 43, 1055. [4] Rosebrock, G.; Elgafy, A.; Beechem, T.; Lafdi, K. Carbon 2005, 43, 3975. [5] Rios, R. V.; Escandell, M. M.; Sabio, M. M.; Reinoso, F. R. Carbon 2006, 44, 1448. [6] Ema, Y.; Ikeya, M.; Okamoto, M. Polymer 2006, 47, 5350. [7] Mesalhy, O.; Lafdi, K.; Elgafy, K. Carbon 2006, 44, 2080.