Synthesis of liebenbergite nano-crystallites from silicate precursor gels prepared by geopolymerization

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概要

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• Silicate precursor gels containing Ni ions were prepared from sodium metasilicate and nickel nitrate solutions by geopolymerization at room temperature. Caustic soda solution was introduced as pH stabilizer. The gels obtained were heat-treated at 700-1400°C for 1 hour. Crystalline phases as well as raw gels were characterized by XRF, TG-DTA, XRD and FE-SEM techniques. NiO contents of the gels increased with increasing pH values. Gels having stoichiometric composition of liebenbergite, Ni2SiO4 were obtained at pH 12.8 with slight Na2O contamination. Na2O contents of the gels also increased gradually with increasing pH values up to 5.87% at pH 12.1 and finally decreased abruptly down to 1.5-2% levels, when exceeding pH 12.6. This trend was very convenient to obtain stoichiometric liebenbergite gels having less Na2O contamination. Two categories of gels were found by TG-DTA in respect to exothermic peaks. Gels prepared at low pH region, ca. 0-5, and high pH region, ca. 13-14, showed no exothermic peaks, indicating that the gels were composed of not inorganic polymers but of simple aggregates of coprecipitates. On the contrary, gels prepared at intermediate pH region, ca. 5-13, showed a sharp exothermic peak, indicating that the gels were composed of inorganic polymers in which atomic order mixing took place due to polycondensation of metal-bearing silica complexes. Accordingly, crystallization temperatures of the gels were lower for the latter that was around 800°C than for the former that was around 1100°C. When heating the gels at elevated temperature, liebenbergite precipitations were observed almost in all gels associated with cristobalite and/or bunsenite according to pH values of gel preparation. The crystalline phases were in nanometer order in size, generally less than 70 nm. The obtained liebenbergite crystallites were platy flakes and 2-dimensionally developed in morphology.

• 日本鉱物科学会の論文
• 2005-08-01

著者

• Vallepu Ramesh

  Yamaguchi Univ. Ube Jpn

• Vallepu Ramesh

  Department Of Advanced Materials Science And Engineering Yamaguchi University

• MIKUNI Akira

  Yamaguchi Prefectural Industrial Technology Institute, Asutopia

• KOMATSU Ryuichi

  Department of Advanced Materials Science and Engineering, Yamaguchi University

• IKEDA Ko

  Department of Advanced Materials Science and Engineering, Yamaguchi University

• Mikuni Akira

  Yamaguchi Prefectural Industrial Technology Institute Asutopia

• Komatsu Ryuichi

  Department Of Advanced Materials Science And Engineering Yamaguchi University

• Ikeda Ko

  Department Of Advanced Materials Science And Engineering Yamaguchi University

• Mikuni Akira

  Yamaguchi Prefectural Industrial Technol. Inst. Ube‐shi

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