Thermal stability of coprecipitated Al 2O 3-SiO 2 xerogels prepared from aluminium nitrate nonahydrate and tetraethylorthosilicate

Kiyoshi Okada, Takahiro Tomita, Yoshikazu Kameshima, Atsuo Yasumori

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4 Citations (Scopus)

Abstract

Amorphous Al 2O 3-SiO 2 xerogels were prepared by coprecipitation and their thermal stability was investigated by powder X-ray diffraction, N 2 gas adsorption and transmission electron microscopy. Xerogels with chemical compositions of 4, 30, 60, 80 and 100 mol%Al 2O 3 were prepared by adding cone. NH 4OH to an ethanol solution of aluminium nitrate nonahydrate (ANN) and tetraethylorthosilicate (TEOS). Deionized water was added to the solution to adjust the molar ratio H 2O/TEOS ≥ 18. The xerogels obtained by calcining at 300°C were heat-treated at 800-1500°C for 2 h at heating and cooling rates of 10°C/min. The specific surface area (S A) of the xerogels heated at high temperatures showed large composition-dependent variations, the samples containing 60 and 80 mol%Al 2O 3 having much higher S A values than the other xerogels. This is attributed to retarding effect of the SiO 2 component for transition into α-Al 2O 3 phase by avoiding direct contact of γ-Al 2O 3 particles. On the other hand, the S A values of the SiO 2-rich and Al 2O 3 xerogels decreased markedly at about 1000-1100°C with increasing of pore radius (r p). This steep decrease in S A and increase of r P are attributed mainly to densification by a viscous flow mechanism accompanied by abrupt particle growth in the SiO 2-rich xerogels and by a particle growth mechanism accompanied by the γ-to-αAl 2O 3 phase transition in the Al 2O 3 xerogel. The thermal stability of the xerogels is compared with those of other previously reported porous ceramics.

Original languageEnglish
Pages (from-to)122-127
Number of pages6
JournalNippon Seramikkusu Kyokai Gakujutsu Ronbunshi/Journal of the Ceramic Society of Japan
Volume108
Issue number2
Publication statusPublished - 2000
Externally publishedYes

Fingerprint

Xerogels
xerogels
nitrates
Nitrates
Thermodynamic stability
thermal stability
aluminum
Aluminum
tetraethoxysilane
aluminum nitrate
Gas adsorption
Deionized water
viscous flow
Viscous flow
densification
Coprecipitation
Chemical analysis
Densification
Specific surface area
X ray powder diffraction

Keywords

  • Aluminosilicate
  • Coprecipitation
  • Porous property
  • Thermal stability
  • Xerogel

ASJC Scopus subject areas

  • Ceramics and Composites

Cite this

@article{230a1fa2526d419194e8939b5e827c5a,
title = "Thermal stability of coprecipitated Al 2O 3-SiO 2 xerogels prepared from aluminium nitrate nonahydrate and tetraethylorthosilicate",
abstract = "Amorphous Al 2O 3-SiO 2 xerogels were prepared by coprecipitation and their thermal stability was investigated by powder X-ray diffraction, N 2 gas adsorption and transmission electron microscopy. Xerogels with chemical compositions of 4, 30, 60, 80 and 100 mol{\%}Al 2O 3 were prepared by adding cone. NH 4OH to an ethanol solution of aluminium nitrate nonahydrate (ANN) and tetraethylorthosilicate (TEOS). Deionized water was added to the solution to adjust the molar ratio H 2O/TEOS ≥ 18. The xerogels obtained by calcining at 300°C were heat-treated at 800-1500°C for 2 h at heating and cooling rates of 10°C/min. The specific surface area (S A) of the xerogels heated at high temperatures showed large composition-dependent variations, the samples containing 60 and 80 mol{\%}Al 2O 3 having much higher S A values than the other xerogels. This is attributed to retarding effect of the SiO 2 component for transition into α-Al 2O 3 phase by avoiding direct contact of γ-Al 2O 3 particles. On the other hand, the S A values of the SiO 2-rich and Al 2O 3 xerogels decreased markedly at about 1000-1100°C with increasing of pore radius (r p). This steep decrease in S A and increase of r P are attributed mainly to densification by a viscous flow mechanism accompanied by abrupt particle growth in the SiO 2-rich xerogels and by a particle growth mechanism accompanied by the γ-to-αAl 2O 3 phase transition in the Al 2O 3 xerogel. The thermal stability of the xerogels is compared with those of other previously reported porous ceramics.",
keywords = "Aluminosilicate, Coprecipitation, Porous property, Thermal stability, Xerogel",
author = "Kiyoshi Okada and Takahiro Tomita and Yoshikazu Kameshima and Atsuo Yasumori",
year = "2000",
language = "English",
volume = "108",
pages = "122--127",
journal = "Nippon Seramikkusu Kyokai Gakujutsu Ronbunshi/Journal of the Ceramic Society of Japan",
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publisher = "Ceramic Society of Japan/Nippon Seramikkusu Kyokai",
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TY - JOUR

T1 - Thermal stability of coprecipitated Al 2O 3-SiO 2 xerogels prepared from aluminium nitrate nonahydrate and tetraethylorthosilicate

AU - Okada, Kiyoshi

AU - Tomita, Takahiro

AU - Kameshima, Yoshikazu

AU - Yasumori, Atsuo

PY - 2000

Y1 - 2000

N2 - Amorphous Al 2O 3-SiO 2 xerogels were prepared by coprecipitation and their thermal stability was investigated by powder X-ray diffraction, N 2 gas adsorption and transmission electron microscopy. Xerogels with chemical compositions of 4, 30, 60, 80 and 100 mol%Al 2O 3 were prepared by adding cone. NH 4OH to an ethanol solution of aluminium nitrate nonahydrate (ANN) and tetraethylorthosilicate (TEOS). Deionized water was added to the solution to adjust the molar ratio H 2O/TEOS ≥ 18. The xerogels obtained by calcining at 300°C were heat-treated at 800-1500°C for 2 h at heating and cooling rates of 10°C/min. The specific surface area (S A) of the xerogels heated at high temperatures showed large composition-dependent variations, the samples containing 60 and 80 mol%Al 2O 3 having much higher S A values than the other xerogels. This is attributed to retarding effect of the SiO 2 component for transition into α-Al 2O 3 phase by avoiding direct contact of γ-Al 2O 3 particles. On the other hand, the S A values of the SiO 2-rich and Al 2O 3 xerogels decreased markedly at about 1000-1100°C with increasing of pore radius (r p). This steep decrease in S A and increase of r P are attributed mainly to densification by a viscous flow mechanism accompanied by abrupt particle growth in the SiO 2-rich xerogels and by a particle growth mechanism accompanied by the γ-to-αAl 2O 3 phase transition in the Al 2O 3 xerogel. The thermal stability of the xerogels is compared with those of other previously reported porous ceramics.

AB - Amorphous Al 2O 3-SiO 2 xerogels were prepared by coprecipitation and their thermal stability was investigated by powder X-ray diffraction, N 2 gas adsorption and transmission electron microscopy. Xerogels with chemical compositions of 4, 30, 60, 80 and 100 mol%Al 2O 3 were prepared by adding cone. NH 4OH to an ethanol solution of aluminium nitrate nonahydrate (ANN) and tetraethylorthosilicate (TEOS). Deionized water was added to the solution to adjust the molar ratio H 2O/TEOS ≥ 18. The xerogels obtained by calcining at 300°C were heat-treated at 800-1500°C for 2 h at heating and cooling rates of 10°C/min. The specific surface area (S A) of the xerogels heated at high temperatures showed large composition-dependent variations, the samples containing 60 and 80 mol%Al 2O 3 having much higher S A values than the other xerogels. This is attributed to retarding effect of the SiO 2 component for transition into α-Al 2O 3 phase by avoiding direct contact of γ-Al 2O 3 particles. On the other hand, the S A values of the SiO 2-rich and Al 2O 3 xerogels decreased markedly at about 1000-1100°C with increasing of pore radius (r p). This steep decrease in S A and increase of r P are attributed mainly to densification by a viscous flow mechanism accompanied by abrupt particle growth in the SiO 2-rich xerogels and by a particle growth mechanism accompanied by the γ-to-αAl 2O 3 phase transition in the Al 2O 3 xerogel. The thermal stability of the xerogels is compared with those of other previously reported porous ceramics.

KW - Aluminosilicate

KW - Coprecipitation

KW - Porous property

KW - Thermal stability

KW - Xerogel

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VL - 108

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JO - Nippon Seramikkusu Kyokai Gakujutsu Ronbunshi/Journal of the Ceramic Society of Japan

JF - Nippon Seramikkusu Kyokai Gakujutsu Ronbunshi/Journal of the Ceramic Society of Japan

SN - 1882-0743

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