Polycrystalline cordierite bodies having the theoretical composition were synthesized from several reagent grade starting materials.
The difference in reaction modes and the mechanisms for cordierite formations from α -quartz or silicic acid as silica source with magnesia and alumina obtained during heat treatment of starting materials by their thermal decompositions was investigated in the firing temperature range of 800℃ to 1400℃.
In order to clarify the difference in effects of small additions of some oxides to the batch mixes on the formation of cordierite, 1,2 or 3wt.% of CaO or $Fe_2O_3$ were added to each batch mix having the theoretical composition, and the same mole % of each oxide was substituted for MgO or $Al_2O_3$ of cordierite composition.
The results have been analyzed by means of several techniques using X-ray diffraction, D.T.A., electron microprove analyzer and microscopic observations.
It was concluded that cordierite formation was initiated at a temperature near 1200℃ by the reaction between spinel and α-cristobalite which were converted by consumption of the starting materials prior to reach the temperature.
Some 60% of cordierite was formed from a batches having the theoretical composition at 1300℃. However, an addition of 1-3% of CaO to the batch mix yielded the same amount of cordierite as above at 1200℃. Addition of $Fe_2O_3$ affected little on the amount of cordierite formation at all temperature ranges studied.
Same effect was found in case of substitution of CaO and $Fe_2O_3$ for MgO and $Al_2O_3$ in the lattice of cordierite structure.
시약급 원료를 사용하여 이론조성의 cordierite 광물상을 합성함에 있어서 silica source로 α-quartz와 silicic acid를 열분해에서 얻은 MgO와 $Al_2O_3$의 혼합물과 반응시켜 800℃에서 1400℃의 온도범위에서 반응과정을 비교 검토하고 cordierite 생성 mechanism을 규명하였다. 또한 첨가제의 효과를 조사하기 위하여 CaO와 $Fe_2O_3$를 각각 1,2,3wt.% 첨가시키고, MgO와 $Al_2O_3$ 대신에 CaO와 $Fe_2O_3$를 각각 1,2,3 mol.% 치환시켜 이들 첨가제가 cordierite 생성에 미치는 영향을 X -선 회절분석, D.T.A.,E.P.M.A. 그리고 현미경 관찰을 통하여 검토하였다.
Cordierite는 1200℃ 부근의 온도에서 출발원료로부터 생성된 α-cristobalite 의 반응으로 시작되어 1300℃ 에서 60% 이상 생성되는데, 1-3%의 CaO를 첨가하면 1200℃ 에서도 이와 같은 양이 생성되는데 비하여, $Fe_2O_3$의 첨가는 cordierite 생성에 별다른 촉진효과를 나타내지 않았으며, CaO와 $Fe_2O_3$를 MgO와 $Al_2O_3$에 대하여 각각 치환한 경우도 전술한 바와 같은 경향을 나타냈다.