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1 Journal of the Korean Ceramic Society Vol. 47, No. 6, pp. 566~571, DOI: /KCERS Effect of Dispersion on Tape Casted Green Sheet Prepared from Bimodal-Type AlN Powders Hong-Soo Choi and Sang-Jin Lee Department of Advanced Materials Science and Engineering, Mokpo National University, Muan , Korea (Received October 11, 2010; Revised October 19, 2010; Accepted October 22, 2010) Bimodal s AlN l ve q x w z y Á s w œw ( ; ; ) ABSTRACT Dispersion behavior of the slurries consisted of bimodal-type AlN powders was examined in non-aqueous solvent system. Azotropic solvent system and copolymer acidic dispersant were applied to the slurries. Measurements of the sedimentation height and the viscosity of the each slurry, and the test of particle size distribution of the each powder sample were conducted as examinations for the dispersion behavior at the various dispersant contents. The bimodal-type particle size distribution was continued after addition of the dispersant and small particle portions were increased as the dispersant content increases. The density of the green sheet was also increased as the dispersant content increases and a green density of g/cm 3 was obtained at the sample prepared from 2.4 wt% dispersant content. The increase of large particle portions resulted in the surface defects of the green sheets. Key words : AlN powder, Dispersion, Bimodal, Tape casting, Slurry 1. AlN,» w, û g w q w qj y»q ƒ š. 1,2) AlN»q w» w l v e q œ š, AlN ƒ» w œ š. 3,4) l v e q œ y w w. 5,6) œ, t w w, ü ùš, x ü w. x y w w ù ³ w w w. t y j ù, y k ƒw» Corresponding author : Sang-Jin Lee [email protected] Tel : Fax : (electrostatic repulsion) y y (steric stabilization)» w w. p št 7,8) l v w» w w, w j k ü s k y š wš, x e w w v w. w k x l 9) v w e. j w e, w, ƒ ƒ w e, w ƒ w w. 9-12) AlN, w s š, w s l v e q œ x,, ƒ w ƒ,»q t j w e. x ƒ, z»q w, w x w s ƒ y j w. x z yw w 1µm ü w AlN w, sƒ 566

2 Bimodal s AlN l ve q x w z 567 l v e q œ w. 4,13), w ù y œ bimodal s ƒ ƒ AlN, bimodal s AlN w l v e q e w w š v w. q bimodal xk s AlN w z l v e q x š w. lw ƒ z bimodal s y w š, w ƒ l v e q x e w š w. 2. x 2.1. AlN p l ve q œ AlN (Hgrade, Tokuyama Co., Japan) p» w w. AlN p g 1 q w k z,» (electrophoretic light scanning spectrophotometer ESL-800, Photal, Japan) w s³ s d w. w» w v Au-Pd gqw x (SEM, Model S3500, Hitachi, Japan) w w l p AlN w l p azotropic y w 4ƒ toluen, N-butyl alcohol, isopropyl alcohol, ethyl alcohol w xw. 14) Azotropic yw ƒ 30 : 30 : 20 : 20 vol% w. copolymer acidic BYK- 111 (DISPERBYK-111, BYK-Chemie Korea Co., Korea) AlN šx» wt% yww x w. ƒ w ƒ AlN, š y š w š, e x d mw š w. x w AlN 60 g 35 g ƒƒ 0, 0.3, 0.6, 0.9, 1.2, 1.5, 1.8, 2.1, 2.4 wt% ƒ g 1 w w. Bimodal s z w» w ƒ w w y w. e x Mistler Twiname w w. 10) 50ml ƒƒ z jš, 120 z e d w, e 3z d s³ w. d s d e x w 3 ew y k z, d (Model DV-II, Brookfield Co., USA) w d w š, s d s w v w z,» w d w x p l v e q x w ƒƒ w (polyvinyl butyral) ƒ (di-butyl phthalate) ƒwš, w l v e q x w. ƒ AlN šx» ƒƒ 8wt% ƒw z, 3 w wš, w ks œ z l v e q x w. w k ƒ x w j» v d w x d w. x x d w z s³ l w. x t k l» w w. 3. š 3.1. p AlN s Fig. 1 ùkü. s³ 1.3 µm 30 µm bimodal s š, SEM j xk š p p sƒw ƒ ü š e d w, Fig. 1. Particle size distribution and SEM micrograph of AlN powder. 47«6y(2010)

3 최홍수 이상진 568 Fig. 3. Fig. 4. Fig. 2. Dispersion behavior of AlN slurries at various dispersant contents. 이 잘 될수록 침전된 입자들의 충전밀도가 높아 침전 높 이가 낮아지는데 기인한다. 또한 미세한 입자일수록 침전 시간이 길며, 장시간 후에도 침전물과 액상의 구분이 뚜렷 하지 않으며 상층액은 불투명한 상태로 지속된다. 일반적 으로 비수계에서의 분산제는 입자의 표면에 고분자 전해 물로 흡착되어 분산상태를 안정화 시켜주기 때문에, 분산 제가 적절하게 흡착될 경우 분산이 원활하게 이루어지며, 분산상태가 안정하게 유지되면 침전속도는 느려지게 된다. 본 연구에서는 분산제의 양을 변화시켜가며, 각 분산제 의 첨가량에 따른 슬러리 내 고상 분말의 침전높이를 관 찰하였으며, 그 결과를 Fig. 2에 나타내었다. 결과에서 보 듯이 48시간 이후에 분산제를 첨가하지 않은 슬러리의 10) 한국세라믹학회지 Change of sedimentation height of AlN slurries at various dispersant contents and setting times. Change of viscosity of AlN slurries at various dispersant contents. AlN 분말이 가장 먼저 침전되었으며, 상층액은 거의 투 명한 상태를 나타내었다. 96시간 이후에는 0.3 wt% 분산 제를 첨가한 슬러리에서 가장 낮은 침전 높이를 보였으 며, 분산제 양이 증가할수록 침전층과 액상층의 구분이 뚜렷하지 않으면서 혼탁한 상층액을 보였다. 시간에 따른 각 슬러리의 침전물의 높이 변화를 Fig. 3에 나타내었다. 0.6 wt%, 0.9 wt% 그리고 1.2 wt%의 침전 거동은 1.5 wt% 와 거의 유사하였고, 1.8 wt%는 2.1 wt%와 유사하여 Fig. 3 의 결과에서는 생략하였다. 앞의 설명과 같이 120시간 이 후의 침전높이 측정결과는 0.3 wt% 분산제가 첨가된 슬 러리가 가장 낮은 침전높이를 나타내었다. 분산제 양이 증가할수록 침전높이는 매우 완만히 증가하는 경향을 나 타내었으나, 침전물과 용액과의 경계가 뚜렷하지는 않았 다. 침전물 상층의 용액은 분산제를 첨가하지 않은 슬러 리를 제외하고는 모두 혼탁한 현상을 보였으며, 혼탁 정 도는 분산제의 첨가량이 많을수록 더욱 증가하였다. 이와 같은 침전거동은 분산제의 양에 따른 슬러리의 점도변화

4 Bimodal s AlN l ve q x w z 569 w, Fig. 4 ùk ü. 0.3 wt% ƒ z w, z ƒ ƒ w w ùkü. z ƒ e y, e d ykw w. e k w» w, ƒ s d Fig. 5 ùkü. ƒw AlN, p w bimodal s. 0.3 wt% ƒ s y w, j ƒ wì j» sƒ. 0.6 wt% ƒ z l j» ƒ bimodal s ùkü. w bimodal s ƒ w ƒw» w, j s» w. w x ƒƒ ƒw x. w ƒ s³, s³ j» w w ùkü. w e e, bimodal xk ƒ w s³ bimodal s w. w w, ƒw bimodal AlN w. w s l v e q x w» w ƒ ƒ ƒ z w e q z, x t x d Fig. 6 Fig. 7 ƒƒ ùkü. ƒw t j wì ³ew w x ùkù x x. 0.3 wt% ƒ j ù, t w x. t w x ƒ ƒw, 2.4 wt% ƒ. x d ƒ ƒx, 2.4 wt% ƒ g/cm 3 x. w ƒx x t w x w, t w x s k, bimodal xk s j ( 10 µm ü ) j x x dw. w z w Fig. 5. Particle size distribution of AlN powder samples from each slurry at various dispersant contents. 47«6y(2010)

5 570 y Á Fig. 6. Photographs of green sheet surfaces prepared from different dispersant contents. Fig. 7. Density change of green sheets prepared from different dispersant contents. (submicron ) ƒw x ƒƒ. l v e q œ x»k š, w, ƒ ƒ w w, bimodal s AlN w z w ƒ w w ƒ w w wš, w s y x y š w. l, yw x k x» w acidic ƒ, ƒ j w w. w wz 4. Bimodal s AlN w l w ƒ w š w, l v e q x y š. 1. azotropic l AlN copolymer acidic 0.3 wt% ƒ w z ƒ x, ƒ w z ƒ ƒ. 2. Bimodal s AlN ƒ z bimodal s xk w, ƒ ƒ j» ƒw š, w. 3. Bimodal s 10 µm ü j x t w x x j d, submicron j» ƒw l v e q x x ƒw. REFERENCES 1. X. J. Luo, B. L. Zhang, W. L. Li, and H. R. Zhuang, Preparation of Aluminum Nitride Green Sheets by Aqueous Tape Casting, Ceram. Int., (2004). 2. L. M. Sheppard, Aluminum Nitride : A Varsatile but Challenging Materials, Am. Ceram. Soc. Bull., 69 [11] (1990). 3. P. Bowen, J. G. Highfield, A. Mocellin, and T. A. Ring, Degradation of Aluminum Nitride Powder in an Aqueous Environment, J. Am. Ceram. Soc., 73 [3] (1990). 4. X. J, Luo, B. L. Zhang, W. L. Li, and H. R. Zhuang, Comparison of Aqueous and Non-Aqueous Tape Casting of Aluminum Nitride Substrates, J. Am. Ceram. Soc., 88 [2] (2005). 5. K. Otsuka, Y. Ohsawa, K. Yamada, and A. Sekibat, A

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