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1 Jurnal f the Krean Ceramic Sciety Vl. 45, N. 5, pp. 303~308, Synthesis f Mullite Pwders by the Geplymer Technique Se Gu Sn, Ji Hyen Lee, Jeng Mi Lee, and Yung D Kim GEOWHA E.S.R Research Center, Chunchen , Krea (Received May 15, 2008; Accepted May 21, 2008) Geplymer Technique w Mullite w Á xá Á½ y» ( ; ) ABSTRACT Mullite precursrs were synthesized with aluminsilicate gels frm mixture f aluminum nitrate and sdium rthsilicate by the geplymer technique at ambient temperature. Then, the gel was heat-treated in air up t 1200 C at intervals f 100 C. Raw and heattreated gels were characterized by TG-DTA, XRD, FTIR, 29 Si MAS-NMR, TEM. The result t examine the crystallizatin f behavir thugh DTA, the synthesized precursrs were crystallized in the temperature range frm 950 C t 1050 C. The XRD results shwed that the gel cmpsitins were begun t crystallize at varius temperature. Als, it was fund that the precursrs f M-4 begun t crystallize at abut 950 C. The M-4 XRD peaks were characterized better than M-1~M-3 at 1000 C. The frmatin temperature f mullite in this study is much lwer than that f previus sl-gel methds, which crystallized at up f 1200 C. TEM investigatins revealed that the sample with 10 nm particle size was btained via heat-treated at 1000 C fr M-4. Key wrds : Mullite, Aluminsilicate gel, Geplymer technique, Crystallizatin behavir, Nan size 1. Mullite w, š» w» ƒ š Al 2 O 3 -SiO 2 š w w w ƒ š. 1)» mullite w, 2) œe, 3-5) -, 5-8) š 9), - w w yw ƒ ywš š ƒ ƒ wš,» w yw w e w ƒ ³ w w š. w 1200 ~ 1300 C y w, g w». Geplymer 3 silic-aluminate inrganic plymer 1978 Davidvits w. 10,11) Crrespnding authr : Se Gu Sn sgsn@hanmail.net Tel : Fax : z, geplymer w w wš.» geplymer 80 C KOH e» metakalin silica w w. geplymer w» w geplymerizatin ù w. 12,13) geplymer»» y ƒ w, w w š y w. w slgel w, û ù l j» silicate w w. 14,15) SiO 2 šƒ g w sl-gel, geplymer technique SiO 2 sdium silicate ù ptassium silicate w. Geplymer technique w mullite w ƒ w precursr w wš û yƒ ƒ w»» sl-gel w w. ƒ silicate aluminum nitrate w aluminsilicate gel w w š w mullite w. 303

2 304 Á xá Á½ Table 1. Experimental Cnditins n the Preparatin f Precursrs Sample Start Materials Si-surce Al-surce [Si 4+ ] ph [Al 3+ ] Injectin methd Si/Al Reactin temp.( C) Stirring M-1 M-2 Sdium silicate slutin 12.7 M-3 Sdium silicate slutin Sdium hydrxide M-4 Sdium rthsilicate >14 Aluminium nitrate [Si] [Al] [Al] [Si] Magnetic stirrer Table 2. Identified Crystalline Phase as a Functin f Heating Temperature Heating temperature( C) N M-1 C C C C C C M-2 Am Am Am Am M M M-3 Am Am M M M M M-4 Am M M M M M C: Cristbalite, Am : Amrphus, M: Mullite 2. x Si œ sdium rthsilicate(2na 2 OSiO 2 1.1H 2 O, Wak) sdium silicate slutin w mullite w mw. Al œ aluminium nitrate(al(no 3 ) 3 9H 2 O, p, Wak) w. x Table 1 ùkü. p Si œ mullite w ph ywš w ww. Si œ ph 12.7, 3.5, >14 w w, ph 12.7 sdium silicate slutin w w, ph 13.5 sdium silicate slutin sdium hydrxide ƒw w. ph >14 sdium rthsilicate w w. Al Si Si Al w. x aluminsilicate gel, e z» 50 C 24 g. gel TGA/DTA(STD 2960, DSC 2910) w 1300 C¾ w w. mw ƒƒ 900 C, 950 C, 1000 C, 1050 C, 1100 C, 1200 C w y w. w XRD z» (PHILIPS, XPERT-PRO) w y w, mullite y w y 29 Si MAS- NMR(Unity INOVA600, Varian) w w. 3. š Geplymer technique w w mullite y y w» w TGA/DTA w, 5 C/min 1300 C¾ w. Fig. 1 ùk ü. Fig. 1 DTA v 100~ 200 C vjƒ ùkû ƒ š, M C~1050 C vj y w ƒ. w TGA v DTA š ƒ 100 C~ 200 C w, 600 C ƒ. DTA š 100 C~200 C vj mullite t k w ƒ, 950 C~ 1050 C w vj w mullite» w q. ƒ 20~30%, M-4ƒ 30% ƒ j ùkþ. Si œ 900 C ~1200 C 5 C/minw w XRD Table 2 Fig. 2 ùkü. Si œ ƒ y w. p Al œ Si œ w M-1 x 900 C~1200 C cristbalite y. ù Si œ Al œ w, e»w w wz

3 Geplymer Technique w Mullite w 305 Fig. 1. Typical TGA/DTA curves f mullite precursr gels; (a) M-1, (b) M-2, (c) M-3, and (d) M-4. w M-2 ~ M-4 x» mullite ƒ. Mullite y ph ùkü. M C, M C l mullite š, w 1200 C¾ w mullite. w ph > 14 M-4 x w y 950 C JCPDS e ( ) w y w. w ƒ geplymerisatin š ƒ. Geplymerisatin š e w w. p 16) geplymer matrix SiO 2 Al 2 O 3 Si Al w š e». ph SiO 2 š yw ³ w mullite ƒ» û mullite ƒ ù ƒ. K. Ikeda û ph w gel w silica alumina yw w w» w, phƒ w gel v ù ke alkali activatin w gel w w aluminsilicate š šwš. y xk 15) Si Al w w ƒ ƒ w w spinel wš mullite e w ù, z š aluminsilicate gel w ƒ spinel 2 e š mullite y» û yƒ ƒ w ƒ. w geplymer technique w w mullite y» w 150 ~ 250 C û. 9,17,18) Fig. 3 w w mullite w w 29 Si MAS- NMR w. š Si-NMR š k 29 45«5y(2008)

4 306 Á xá Á½ Fig. 2. X-ray diffractin results f heat-treated samples prepared in varius reactin cnditins; (a) M-1, (b) M-2, (c) M-3, and (d) M-4. w w. Q0( 66~ 73 ppm) islated tetrahedra, Q1( 74 ~ 78 ppm) chain end Fig Si MAS-NMR spectra f the precursr gels(raw) and calcined at 1000 C. trup tetrahedra, Q2( 83 ~ 88 ppm) middle grups, Q3( 95 ~ 103 ppm) branching sites, Q4( 103~115 ppm) crss-linking sites ùkü. 29 Si MAS-NMR M-2 M-4 as-prepared (M-2 Raw, M-4 Raw) 1000 C(M , M ) w w ww ww. Fig. 3 M-2, M-2 asprepared M w, Fig. 2. M C pattern ƒ mullite ùkü qp y. w M- 2 as-prepared 1000 C r 29 Si MAS- NMR qp y 99.3 ppm vjƒ 110 ppm vj eƒ w ƒ. M-4 29 Si MAS-NMR qp XRD pattern y ew y w ƒ. M-4 as-prepared M ppm 97.1 ppm vjƒ. M M-4 asprepared 78.2 ppm 97.1 ppm vj û. w 29 Si MAS-NMR qp 86.8 ppm, 90.0 w wz

5 Geplymer Technique에 의한 Mullite 분말의 합성 307 Fig. 4. The electrn diffractin pattern(a) and the bright-field image(b) f the heat-treated aluminsilicate gel at 1000C. ppm, 94.0 ppm, ppm에서 확인되었다. 여기에서 앞의 86.8 ppm, 90.0 ppm, 94.0 ppm이 세 피크는 mullite의 전형적인 피크이며, 109. ppm은 Q4(1Al)를 나타내는 aluminsilicate 상의 Si MAS-NMR 피크이다. M-4 as-prepared의 78.6 ppm와 99.3 ppm피크는 모두 mullite와 aluminsilicate 상으로 전이되었음을 알 수 있었 다. Fig. 4.는 합성된 mullite 전구체(M-4)를 1000 C로 열처 리한 시료의 TEM 사진을 나타낸 것이다. 사진에서와 같 이 결정성 mullite 입자의 크기는 약 10 nm의 크기를 갖 는 것을 확인할 수가 있으며, 결정입자가 구형임을 알 수 가 있었다. 또한 전자회절패턴(a)의 이미지는 1000 C에서 열처리된 시료가 120면의 결정성의 mullite임을 나타내고 있다. 17) 결 론 Geplymer technique에 의한 합성과 저온형 mullite의 합성이 상온에서 mullite 전구체 가능하였다. DTA를 통한 전구체의 결정성 거동 조사에서, 합성된 전구체는 950 C 에서 1050 C의 온도범위에서 결정화되었다. XRD 분석결 과 전구체는 다양한 온도에서 결정화 되는 것을 확인할 수 있었으며, 특히 M-4의 경우에는 950 C부터 mullite 결 정화가 진행됨을 알 수가 있었다. 또한 1000 C에서의 M-4 의 결정성은 M-1~M-3보다 우수한 것을 알 수가 있었다. 이러한 결과는 기존의 sl-gel 법 등에 의해서 합성된 gel 의 결정화 온도보다 150~250 C정도 낮은 결과이었다. TEM 분석을 통하여 1000 C에서 열처리된 M-4의 mullite 입자는 결정성의 10 nm의 크기임을 확인하였다. Acknwledgment 본 연구는 에너지관리공단 에너지자원기술개발사업 (N.2006-R-RU11-P )지원으로 며, 이에 감사드립니다. 수행되었으 REFERENCES 1. H. Schneider, J. Schreuer, and B. Hildmann, Structure and Prperties f Mullite-A Review, J. Eur. Ceram. Sc., (2008). 2. O. Byrgis-Mntes, R, Mren, Maria T. Clmer, and J. C. Farinas, Synthesis f Mullite Pwders Thrugh a Suspensin Cmbustin Prcess, J. Am. Ceram. Sc., 89 [2] (2006). 3. G. P. Thim, C. A. Bertran, V. E. Barlette, M. I. F. Maced, and M. A. S. Oliverira, Experimental and Mnte Carl Simulatin: the Rle f Urea in Mullite Synthesis, J. Eur. Ceram. Sc., (2001). 4. S. S. Sueyshi and C. A. Cntreras St, Fine Pure Mullite Pwder by Hmgeneus Precipitatin, J. Eur. Ceram. Sc., (1998). 5. S. Satshi, C. Cntreras, H. Juarez, A. Aguilera, and J. Serrat, Hmgeneus Precipitatin and Thermal Phase Transfrmatin f Mullite Ceramic Precursr, Int. J. Inrg. Mater., (2001). 6. D. Amutharani and F. D. Gnanam, Lw Temperature Pressureless Sintering f Sl-gel Derived Mullite, Mater. Sci. Eng., A (1999). 7. G. M. Anilkumar, U. S. Hareesh, A. D. Damdaran, and K. G. K. Warrier, Effect f Seeds n the Frmatin f Sl-gel Mullite, Ceram. Intern., (1997). 8. J. Parmentier and S. Vilmint, Influence f Transitin Metal Oxides n Sl-gel Mullite Crystallizatin, J. Ally. Cmpd., (1998). 9. L. B. Kng, T. S. Zhang, Y. Z. Chen, J. Ma, F. Bey, and H. Huang, Micrstructural Cmpsite Mullite Derived frm Oxides Via a High-energy Ball Milling Prcess, Ceram. Intern., (2004). 10. J. Davidvits, Geplymers and Geplymeric Materials, J. Therm. Anal., (1989). 11. J. Davidvits, Inrganic Plymeric New Materials, J. 제 45 권 제 5호(2008)

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