DOI: 10.1111/j.1151-2916.1996.tb08527.x. Porous Silica‐Coated α‐Fe<sub>2</sub>O<sub>3</sub> Ceramics for Humidity Measurement at Elevated Temperature

Porous Silica‐Coated α‐Fe2O3 Ceramics for Humidity Measurement at Elevated Temperature

10.1111/j.1151-2916.1996.tb08527.x

Crossref journal-article

Wiley

Journal of the American Ceramic Society (311)

Abstract

Porous α‐Fe2O3 powder obtained from topotactic decomposition of α‐FeOOH was dispersed in a tetraethyl orthosili‐cate solution. Amorphous silica was coated on the surface of α‐Fe2O3 grains, followed by gelation and sintering. The N2sorption measurement indicates that the pore coalescence is strongly suppressed by coating. For instance, the coated sample sintered at 800°C has a specific surface area of 145.8 m2/g, much greater than the uncoated one, 5.035 m2/g. Furthermore, the hysteresis isotherm implies that thepores of the coated sample have an ink‐bottle type structure. There are O and Si traces in the XPS survey scan, while no Fe peak is found, which confirms that the α‐Fe2O3 grain is totally covered by silica. Organic radicals are also evident in the detail scan of the C1s peak of the fresh fractured surface. The XRD analysis highlights that the coated ceramic is composed of α‐Fe2O3 and amorphous silica. Because of the coating limitation on grain growth, sintering below 950°C hardly increases the grain size as compared with the starting powder, in terms of Scherrer's equation. The HRTEM images of the uncoated and coated samples display a clear layer of the amorphous coating on highly porous grains. Many pores in the 2–5 nm size range seem to be connected in the lattice matrix. The pore number and volume are greatly decreased after sintering, but the silica coating weakens this effect. The complex impedance of the coated sample with porous RuO2 electrode was investigated in the frequency and temperature ranges of 1 Hz‐1 MHz and 20°–400°C, respectively. Artificial dry air was bubbled through deionized water or analytical‐purity ethanol to yield wet air or ethanol vapor condition. The sensitivities, defined as the ratio between impedance under a test and dry air conditions, are 30 for 2.8% water vapor and 2 for 9.3% ethanol vapor at 200°C. A high ethanol vapor sensitivity above 200°C is explained as an “on‐site” water vapor effect arising from the ethanol combustion on a silica catalyst. Various gases like CH4, CO, NOx, and NO2 were introduced into dry and wet air at elevated temperatures. No cross‐sensitivity was found for the gas concentrations up to 5000 ppm. A model of the porous coating structure is proposed for a reason of high humidity sensitivity without gas cross‐sensitivity.

Bibliography

Sun, H., Cantalini, C., Faccio, M., Pelino, M., Catalano, M., & Tapfer, L. (1996). Porous SilicaâCoated Î±âFe2O3 Ceramics for Humidity Measurement at Elevated Temperature. Journal of the American Ceramic Society, 79(4), 927â937. Portico.

Authors 6

Hong‐Tao Sun (first)
Carlo Cantalini (additional)
Marco Faccio (additional)
Mario Pelino (additional)
Massimo Catalano (additional)
Leander Tapfer (additional)

References 38 Referenced 62

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Dates

Type	When
Created	19 years, 11 months ago (Sept. 28, 2005, 4:07 a.m.)
Deposited	1 year, 9 months ago (Nov. 23, 2023, 12:32 a.m.)
Indexed	1 month, 4 weeks ago (July 7, 2025, 9:07 a.m.)
Issued	29 years, 5 months ago (April 1, 1996)
Published	29 years, 5 months ago (April 1, 1996)
Published Online	19 years, 11 months ago (Sept. 28, 2005)
Published Print	29 years, 5 months ago (April 1, 1996)

Funders 0

None

BibTeX

@article{Sun_1996, title={Porous Silica‐Coated α‐Fe2O3 Ceramics for Humidity Measurement at Elevated Temperature}, volume={79}, ISSN={1551-2916}, url={http://dx.doi.org/10.1111/j.1151-2916.1996.tb08527.x}, DOI={10.1111/j.1151-2916.1996.tb08527.x}, number={4}, journal={Journal of the American Ceramic Society}, publisher={Wiley}, author={Sun, Hong‐Tao and Cantalini, Carlo and Faccio, Marco and Pelino, Mario and Catalano, Massimo and Tapfer, Leander}, year={1996}, month=apr, pages={927–937} }

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  "URL": "http://dx.doi.org/10.1111/j.1151-2916.1996.tb08527.x",
  "relation": {},
  "ISSN": [
    "0002-7820",
    "1551-2916"
  ],
  "subject": [],
  "container-title-short": "Journal of the American Ceramic Society",
  "published": {
    "date-parts": [
      [
        1996,
        4
      ]
    ]
  }
}