Abstract

Colloidal silica films on glass produced by withdrawal from colloidal baths are of value as antireflection coatings. The effect of particle size on the refractive index and density of these films was determined, and the optimum particle diameter for maximum transmittance of solar radiation through glass was estimated at 45 nm. Mixed colloidal carbon and silica films produced by the same means were also studied. These films are useful as solar selective absorbing coatings when deposited on copper. The optical constants of the mixed colloidal films were determined and the results compared with the predictions of the Maxwell Garnett theory. The effect on the thermal efficiency of solar absorbing coatings of a variation in the carbon-to-silica weight ratio was determined.

© 1988 Optical Society of America

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References

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  1. H. R. Moulton, “Composition for Reducing the Reflection of Light,” U.S. Patent2,601,123 (June1952).
  2. K. Cathro, D. Constable, T. Solaga, “Silica Low-Reflection Coatings for Collector Covers, by a Dip-Coating Process,” Sol. Energy 32, 573 (1984).
    [CrossRef]
  3. J. J. Zybert, D. R. McKenzie, “Colloidally Deposited High-Temperature Solar Selective Surfaces,” Appl. Opt. 20, 4051 (1981).
    [CrossRef] [PubMed]
  4. D. R. McKenzie, J. J. Zybert, “Optimization of Solar Selectivity in Colloidally Produced Solar Selective Coatings,” Thin Solid Films 85, 191 (1981).
    [CrossRef]
  5. J. J. Zybert, D. R. McKenzie, “Enhancement of Absorptance of Selective Coatings with Colloidal Films,” Sol. Energy Mater. 6, 107 (1981).
    [CrossRef]
  6. S. P. Chow, G. L. Harding, R. E. Collins, “Degradation of All-Glass Evacuated Solar Collector Tubes,” Sol. Energy Mater. 12, 1 (1985).
    [CrossRef]
  7. The carbon aquasol contained 20% wt./wt. Degussa special black 4, 25-nm particle size, and 4% wt./wt. Teric N30 (ICI Australia) as a dispersant.
  8. Catoleum PR480, 5-nm particle size.
  9. O. S. Heavens, Optical Properties of Thin Solid Films (Dover, New York, 1955).
  10. R. C. McPhedran, L. C. Botten, D. R. McKenzie, R. P. Netterfield, “Unambiguous Determination of Optical Constants of Absorbing Films by Reflectance and Transmittance Measurements,” Appl. Opt. 23, 1197 (1984).
    [CrossRef] [PubMed]
  11. E. T. Arakawa, M. W. Williams, T. Inali, “Optical Properties of Arc-Evaporated Carbon Films Between 0.6 and 3.8 eV,” J. Appl. Phys. 48, 3176 (1977).
    [CrossRef]
  12. D. R. McKenzie, R. C. McPhedran, N. Savvides, L. C. Botten, “Properties and Structure of Amorphous Hydrogenated Carbon Films,” Philos. Mag. B48, 341 (1983).

1985 (1)

S. P. Chow, G. L. Harding, R. E. Collins, “Degradation of All-Glass Evacuated Solar Collector Tubes,” Sol. Energy Mater. 12, 1 (1985).
[CrossRef]

1984 (2)

1983 (1)

D. R. McKenzie, R. C. McPhedran, N. Savvides, L. C. Botten, “Properties and Structure of Amorphous Hydrogenated Carbon Films,” Philos. Mag. B48, 341 (1983).

1981 (3)

J. J. Zybert, D. R. McKenzie, “Colloidally Deposited High-Temperature Solar Selective Surfaces,” Appl. Opt. 20, 4051 (1981).
[CrossRef] [PubMed]

D. R. McKenzie, J. J. Zybert, “Optimization of Solar Selectivity in Colloidally Produced Solar Selective Coatings,” Thin Solid Films 85, 191 (1981).
[CrossRef]

J. J. Zybert, D. R. McKenzie, “Enhancement of Absorptance of Selective Coatings with Colloidal Films,” Sol. Energy Mater. 6, 107 (1981).
[CrossRef]

1977 (1)

E. T. Arakawa, M. W. Williams, T. Inali, “Optical Properties of Arc-Evaporated Carbon Films Between 0.6 and 3.8 eV,” J. Appl. Phys. 48, 3176 (1977).
[CrossRef]

Arakawa, E. T.

E. T. Arakawa, M. W. Williams, T. Inali, “Optical Properties of Arc-Evaporated Carbon Films Between 0.6 and 3.8 eV,” J. Appl. Phys. 48, 3176 (1977).
[CrossRef]

Botten, L. C.

R. C. McPhedran, L. C. Botten, D. R. McKenzie, R. P. Netterfield, “Unambiguous Determination of Optical Constants of Absorbing Films by Reflectance and Transmittance Measurements,” Appl. Opt. 23, 1197 (1984).
[CrossRef] [PubMed]

D. R. McKenzie, R. C. McPhedran, N. Savvides, L. C. Botten, “Properties and Structure of Amorphous Hydrogenated Carbon Films,” Philos. Mag. B48, 341 (1983).

Cathro, K.

K. Cathro, D. Constable, T. Solaga, “Silica Low-Reflection Coatings for Collector Covers, by a Dip-Coating Process,” Sol. Energy 32, 573 (1984).
[CrossRef]

Chow, S. P.

S. P. Chow, G. L. Harding, R. E. Collins, “Degradation of All-Glass Evacuated Solar Collector Tubes,” Sol. Energy Mater. 12, 1 (1985).
[CrossRef]

Collins, R. E.

S. P. Chow, G. L. Harding, R. E. Collins, “Degradation of All-Glass Evacuated Solar Collector Tubes,” Sol. Energy Mater. 12, 1 (1985).
[CrossRef]

Constable, D.

K. Cathro, D. Constable, T. Solaga, “Silica Low-Reflection Coatings for Collector Covers, by a Dip-Coating Process,” Sol. Energy 32, 573 (1984).
[CrossRef]

Harding, G. L.

S. P. Chow, G. L. Harding, R. E. Collins, “Degradation of All-Glass Evacuated Solar Collector Tubes,” Sol. Energy Mater. 12, 1 (1985).
[CrossRef]

Heavens, O. S.

O. S. Heavens, Optical Properties of Thin Solid Films (Dover, New York, 1955).

Inali, T.

E. T. Arakawa, M. W. Williams, T. Inali, “Optical Properties of Arc-Evaporated Carbon Films Between 0.6 and 3.8 eV,” J. Appl. Phys. 48, 3176 (1977).
[CrossRef]

McKenzie, D. R.

R. C. McPhedran, L. C. Botten, D. R. McKenzie, R. P. Netterfield, “Unambiguous Determination of Optical Constants of Absorbing Films by Reflectance and Transmittance Measurements,” Appl. Opt. 23, 1197 (1984).
[CrossRef] [PubMed]

D. R. McKenzie, R. C. McPhedran, N. Savvides, L. C. Botten, “Properties and Structure of Amorphous Hydrogenated Carbon Films,” Philos. Mag. B48, 341 (1983).

D. R. McKenzie, J. J. Zybert, “Optimization of Solar Selectivity in Colloidally Produced Solar Selective Coatings,” Thin Solid Films 85, 191 (1981).
[CrossRef]

J. J. Zybert, D. R. McKenzie, “Enhancement of Absorptance of Selective Coatings with Colloidal Films,” Sol. Energy Mater. 6, 107 (1981).
[CrossRef]

J. J. Zybert, D. R. McKenzie, “Colloidally Deposited High-Temperature Solar Selective Surfaces,” Appl. Opt. 20, 4051 (1981).
[CrossRef] [PubMed]

McPhedran, R. C.

R. C. McPhedran, L. C. Botten, D. R. McKenzie, R. P. Netterfield, “Unambiguous Determination of Optical Constants of Absorbing Films by Reflectance and Transmittance Measurements,” Appl. Opt. 23, 1197 (1984).
[CrossRef] [PubMed]

D. R. McKenzie, R. C. McPhedran, N. Savvides, L. C. Botten, “Properties and Structure of Amorphous Hydrogenated Carbon Films,” Philos. Mag. B48, 341 (1983).

Moulton, H. R.

H. R. Moulton, “Composition for Reducing the Reflection of Light,” U.S. Patent2,601,123 (June1952).

Netterfield, R. P.

Savvides, N.

D. R. McKenzie, R. C. McPhedran, N. Savvides, L. C. Botten, “Properties and Structure of Amorphous Hydrogenated Carbon Films,” Philos. Mag. B48, 341 (1983).

Solaga, T.

K. Cathro, D. Constable, T. Solaga, “Silica Low-Reflection Coatings for Collector Covers, by a Dip-Coating Process,” Sol. Energy 32, 573 (1984).
[CrossRef]

Williams, M. W.

E. T. Arakawa, M. W. Williams, T. Inali, “Optical Properties of Arc-Evaporated Carbon Films Between 0.6 and 3.8 eV,” J. Appl. Phys. 48, 3176 (1977).
[CrossRef]

Zybert, J. J.

J. J. Zybert, D. R. McKenzie, “Colloidally Deposited High-Temperature Solar Selective Surfaces,” Appl. Opt. 20, 4051 (1981).
[CrossRef] [PubMed]

D. R. McKenzie, J. J. Zybert, “Optimization of Solar Selectivity in Colloidally Produced Solar Selective Coatings,” Thin Solid Films 85, 191 (1981).
[CrossRef]

J. J. Zybert, D. R. McKenzie, “Enhancement of Absorptance of Selective Coatings with Colloidal Films,” Sol. Energy Mater. 6, 107 (1981).
[CrossRef]

Appl. Opt. (2)

J. Appl. Phys. (1)

E. T. Arakawa, M. W. Williams, T. Inali, “Optical Properties of Arc-Evaporated Carbon Films Between 0.6 and 3.8 eV,” J. Appl. Phys. 48, 3176 (1977).
[CrossRef]

Philos. Mag. (1)

D. R. McKenzie, R. C. McPhedran, N. Savvides, L. C. Botten, “Properties and Structure of Amorphous Hydrogenated Carbon Films,” Philos. Mag. B48, 341 (1983).

Sol. Energy (1)

K. Cathro, D. Constable, T. Solaga, “Silica Low-Reflection Coatings for Collector Covers, by a Dip-Coating Process,” Sol. Energy 32, 573 (1984).
[CrossRef]

Sol. Energy Mater. (2)

J. J. Zybert, D. R. McKenzie, “Enhancement of Absorptance of Selective Coatings with Colloidal Films,” Sol. Energy Mater. 6, 107 (1981).
[CrossRef]

S. P. Chow, G. L. Harding, R. E. Collins, “Degradation of All-Glass Evacuated Solar Collector Tubes,” Sol. Energy Mater. 12, 1 (1985).
[CrossRef]

Thin Solid Films (1)

D. R. McKenzie, J. J. Zybert, “Optimization of Solar Selectivity in Colloidally Produced Solar Selective Coatings,” Thin Solid Films 85, 191 (1981).
[CrossRef]

Other (4)

The carbon aquasol contained 20% wt./wt. Degussa special black 4, 25-nm particle size, and 4% wt./wt. Teric N30 (ICI Australia) as a dispersant.

Catoleum PR480, 5-nm particle size.

O. S. Heavens, Optical Properties of Thin Solid Films (Dover, New York, 1955).

H. R. Moulton, “Composition for Reducing the Reflection of Light,” U.S. Patent2,601,123 (June1952).

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Figures (9)

Fig. 1
Fig. 1

Dependence of the thickness of colloidal silica films on the rate of withdrawal from the bath for Catoleum 1030 and 7604 sols of 16- and 75-nm diameter, respectively.

Fig. 2
Fig. 2

Effect of particle size on the refractive index and density of colloidal silica films.

Fig. 3
Fig. 3

Minimum reflectance at 650 nm and the solar transmittance of colloidal silica films on glass as a function of silica particle size: ○ show data from Cathro et al.2

Fig. 4
Fig. 4

Electron micrograph of the Catoleum 1030 silica sol of 16 ± 3-nm diameter.

Fig. 5
Fig. 5

Electron micrograph of the Catoleum 7604 silica sol of 75 ± 9-nm diameter.

Fig. 6
Fig. 6

Variation of refractive index with wavelength for a colloidal film of mixed carbon and silica particles in the ratio 3:1 by weight. The lines are theoretical calculations based on the Maxwell Garnett theory. The points are the results of the Bivariate method. The solid line is calculated assuming amorphous carbon particles, while the dashed line is calculated assuming amorphous hydrogenated carbon particles.

Fig. 7
Fig. 7

As in Fig. 6, except for extinction coefficient k.

Fig. 8
Fig. 8

Electron micrograph of a silica-carbon mixed colloidal film. The large particles are 25-nm carbon particles, while the smaller particles are 5-nm silica particles.

Fig. 9
Fig. 9

Thermal efficiency am as a function of film thickness for various C/SiO2 weight ratios.

Tables (2)

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Table I Details of the Silica Sols

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Table II Details of Bath Composition

Equations (2)

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R m = n 1 2 - n 2 2 ( n 1 2 + n 1 n 2 ) 2 ,
a m = a s - e t σ T 4 G ,

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