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Title: Sol-gel route to the tunneled manganese oxide cryptomelane

Abstract

The sol-gel reaction between KMnO{sub 4} and fumaric acid in a 3:1 mole ratio generates a flocculant gel that serves as a precursor to the tunneled manganese oxide, cryptomelane. The elemental composition of sol-gel cryptomelane has been determined to be K{sub 0.12}MnO{sub 2.0-} (H{sub 2}O){sub 0.09}. Further characterization has been performed using powder X-ray diffraction, scanning electron microscopy, and Auger electron spectroscopy. The sol-gel process is heavily dependent on reactant concentration. Solutions that are too concentrated produce the layered manganese oxide birnessite, whereas overly dilute reactions yield mixtures of cryptomelane and Mn{sub 2}O{sub 3}. The preference for cryptomelane over birnessite correlates with low potassium content in the gel. The sol-gel procedure for synthesizing cryptomelane is not easily transferred to the preparation of analogous manganese oxides with different tunnel cations. Reactions that employ permanganates other than KMnO{sub 4} generally yield Mn{sub 2}O{sub 3}, with cryptomelane being a minor product at best. Thermal analyses of cryptomelane gels indicate that calcination proceeds through a series of stages that involve loss of water, loss of residual organics, conversion to cryptomelane, and finally degradation to Mn{sub 3}O{sub 4}. The extraction of potassium ions from sol-gel cryptomelane by various foreign cations is minimal, with the lossmore » of K{sup +} being on the order of 10%. 49 refs., 7 figs., 3 tabs.« less

Authors:
;  [1]; ;  [2]
  1. Connecticut College, New London, CT (United States)
  2. Univ. of Connecticut, Storr, CT (United States)
Publication Date:
OSTI Identifier:
569179
Resource Type:
Journal Article
Journal Name:
Chemistry of Materials
Additional Journal Information:
Journal Volume: 9; Journal Issue: 3; Other Information: PBD: Mar 1997
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 40 CHEMISTRY; CALCINATION; CATIONS; FUMARIC ACID; MANGANESE OXIDES; PERMANGANATES; SCANNING ELECTRON MICROSCOPY; SOL-GEL PROCESS; X-RAY DIFFRACTION; CHEMICAL COMPOSITION; AUGER ELECTRON SPECTROSCOPY; SYNTHESIS; CHEMICAL REACTIONS; CHEMICAL REACTION YIELD; POTASSIUM; POROSITY; STOICHIOMETRY; MOLECULAR STRUCTURE; VALENCE; HOLLANDITE; STRUCTURAL CHEMICAL ANALYSIS

Citation Formats

Ching, S, Roark, J L, Duan, N, and Suib, S L. Sol-gel route to the tunneled manganese oxide cryptomelane. United States: N. p., 1997. Web. doi:10.1021/cm960460k.
Ching, S, Roark, J L, Duan, N, & Suib, S L. Sol-gel route to the tunneled manganese oxide cryptomelane. United States. doi:10.1021/cm960460k.
Ching, S, Roark, J L, Duan, N, and Suib, S L. Sat . "Sol-gel route to the tunneled manganese oxide cryptomelane". United States. doi:10.1021/cm960460k.
@article{osti_569179,
title = {Sol-gel route to the tunneled manganese oxide cryptomelane},
author = {Ching, S and Roark, J L and Duan, N and Suib, S L},
abstractNote = {The sol-gel reaction between KMnO{sub 4} and fumaric acid in a 3:1 mole ratio generates a flocculant gel that serves as a precursor to the tunneled manganese oxide, cryptomelane. The elemental composition of sol-gel cryptomelane has been determined to be K{sub 0.12}MnO{sub 2.0-} (H{sub 2}O){sub 0.09}. Further characterization has been performed using powder X-ray diffraction, scanning electron microscopy, and Auger electron spectroscopy. The sol-gel process is heavily dependent on reactant concentration. Solutions that are too concentrated produce the layered manganese oxide birnessite, whereas overly dilute reactions yield mixtures of cryptomelane and Mn{sub 2}O{sub 3}. The preference for cryptomelane over birnessite correlates with low potassium content in the gel. The sol-gel procedure for synthesizing cryptomelane is not easily transferred to the preparation of analogous manganese oxides with different tunnel cations. Reactions that employ permanganates other than KMnO{sub 4} generally yield Mn{sub 2}O{sub 3}, with cryptomelane being a minor product at best. Thermal analyses of cryptomelane gels indicate that calcination proceeds through a series of stages that involve loss of water, loss of residual organics, conversion to cryptomelane, and finally degradation to Mn{sub 3}O{sub 4}. The extraction of potassium ions from sol-gel cryptomelane by various foreign cations is minimal, with the loss of K{sup +} being on the order of 10%. 49 refs., 7 figs., 3 tabs.},
doi = {10.1021/cm960460k},
journal = {Chemistry of Materials},
number = 3,
volume = 9,
place = {United States},
year = {1997},
month = {3}
}