Rietveld 정밀화법과 SEM-EDS 분석에 의한 DPF용 코디어라이트 하니컴 세라믹스의 결정성장 과정 분석 = Characterization of crystal phase evolution in cordierite honeycomb for diesel particulate filter by using rietveld refinement and SEM-EDS methods

국문 초록 (Abstract)

코디어라이트(Mg₂Al₄Si₅O₁₈) 하니컴 세라믹스의 대표적 응용분야는 자동차 배기가스 정화용 필터(diesel particulate filter(DPF))이다. 천연광물, 조공제, 유기바인더를 혼합한 슬러리를 압출하여 DPF용 하니컴 코디어라이트를 성형한 후 980~1450℃ 범위에서 소결하였다. 소결온도에 따른 결정상(indialite, cordierite, cristobalite, alumina, spinel, mullite, pro-enstatite)의 형성과정을 XRD Rietveld 정밀화법을 이용하여 정량분석 하였다. 동시에, 세라믹 에칭(etching) 방법으로 소결 시료 표면의 비정질상을 제거한 후 SEM/EDS법을 사용하여 결정상들의 형상과 조성을 확인하였다. 이들 결과로부터 DPF 하니컴에서 결정상 형성 과정을 명확히 밝힐 수 있었다. 또한, DPF 하니컴의 소결온도에 따른 열팽창계수(linear coefficient of thermal expansion, CTE) 변화를 분석하였고, 결정상의 정량분석결과를 바탕으로 계산된 CTE와 비교하였다. 소결된 DPF 하니컴 내의 결정상들이 CTE 특성에 미치는 영향을 고찰하였다.

다국어 초록 (Multilingual Abstract)

Diesel particulate filter (DPF) is a typical application field of cordierite (Mg₂Al₄Si₅O₁₈) honeycomb. Green body for DPF honeycomb was extruded using slurry paste and sintered at the temperature range of 980~1450℃. Quantitative crystal phase analysis was carried out by using Rietveld refinement method for powder XRD data. In conjunction with the quantitative Rietveld analysis, SEM-EDS analysis was carried for the crystal phases (indialite, cordierite, cristobalite, alumina, spinel, mullite, pro-enstatite). After removing amorphous phase on the sintered surfaces by chemical etching method, the shape and composition of the crystal phases can be clearly identified by SEM-EDS method. By combining the Rietveld refinement method and SEM-EDS analysis, crystal phase evolution process in DPF cordierite ceramics could be clarified. In addition, the coefficient of thermal expansion (CTE) of the DPF honeycombs were measured and compared with the calculated CTEs based on the quantitative crystal phase analysis results.

참고문헌 (Reference)

1 D. L. Evans, "Thermal expansions and chemical modifications of cordierite" 63 : 629-, 1980

2 D. Hugh-Jones, "Thermal expansion of MgSiO3 and FeSiO3 ortho-and clinopyroxenes" 82 : 689-, 1997

3 J. L. Schlenker, "Thermal expansion coefficients for indialite, emerald, and beryl" 1 : 243-, 1977

4 E.P. Meagher, "The polymorphism of cordierite II : The crystal structure of indialite" 15 : 43-, 1977

5 A. Putnis, "The mechanism and kinetics of Al, Si ordering in Mg-cordierite" 68 : 60-, 1983

6 G. W. Brindley, "The kaolinite-mullite reaction series : II. Metakaolin" 42 : 315-, 1959

7 G. W. Brindley, "The kaolinite-mullite reaction series : I. A survey of outstanding problems" 42 : 311-, 1959

8 A. Putnis, "The distortion index in anhydrous Mg-Cordierite" 74 : 135-, 1980

9 A. M. Efremov, "Texture coefficients for the simulation of cordierite thermal expansion : A comparison of different approaches" 31 : 281-, 2011

10 R. Goren, "Synthesis of cordierite powder from talc, diatomite and alumina" 32 : 407-, 2006

11 M. -A Son, "Structural origin of negative thermal expansion of cordierite honeycomb ceramics and crystal phase evolution with sintering temperature" 39 : 2484-, 2019

12 Giovanni Bruno, "Simultaneous determination of high-temperature crystal structure and texture of synthetic porous cordierite" International Union of Crystallography (IUCr) 50 (50): 749-762, 2017

13 T.R. Boger, "Porous ceramic honeycomb articles and methods for making the same, WO/2012/074833"

14 D. Redaoui, "Phase formation and crystallization kinetics in cordierite ceramics prepared from kaolinite and magnesia" 44 : 3649-, 2018

15 G. Bruno, "On the stress-free lattice expansion of porous cordierite" 58 : 1994-, 2010

16 M.L. Stewart, "Fuel Efficient Diesel Particulate Filter (DPF) Modeling and Development" Pacific Northwest National Laboratory 2010

17 G.A. Merkel, "Fabrication of low thermal expansion high porosity cordierite body, US Patent 5258150 A"

18 O. A. Al-Harbi, "Fabrication and characterization of single phase cordierite honeycomb monolith with porous wall from natural raw materials as catalyst support" 41 : 3526-, 2015

19 K. -W. Chae, "Effect of sintering atmosphere on the crystallizations, porosity, and thermal expansion coefficient of cordierite honeycomb ceramics" 47 : 19526-, 2021

20 M. Katayama, "Effect of particle size of tabular talc powders on crystal orientation and sintering of cordierite ceramics" 121 : 934-, 2013

21 T. Watkins, "Durability of diesel engine particulate filters" 2011

22 C. Bubeck, "Direction dependent mechanical properties of extruded cordierite honeycombs" 29 : 3113-, 2009

23 C. Bubeck, "Direction dependent mechanical properties of extruded cordierite honeycombs" 29 : 3113-, 2009

24 E. P. de Almeida, "Cordierite obtained from compositions containing kaolin waste, talc and magnesium oxide" 44 : 1719-, 2018

25 W. Schreyer, "Compositions and structural states of anhydrous Mg-cordierites : A re-investigation of the central part of the system MgO-Al2O3-SiO2" 2 : 324-, 1961