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Ultrasonic Characterization of SOL/GEL Processing

Published online by Cambridge University Press:  21 February 2011

S. Chiou
Affiliation:
Department of Engineering Science and Mechanics The Pennsylvania State University, University Park, PA 16802
H. T. Hahna
Affiliation:
Department of Engineering Science and Mechanics The Pennsylvania State University, University Park, PA 16802
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Abstract

The sol/gel process has recently received attention because it enables the production of pure and homogeneous glass without external heating, eliminating the high processing temperatures needed in conventional methods. A disadvantage of the process is that if the rate of evaporation during syneresis is too high, cracking due to mechanical shrinkage can be extensive. A slower evaporation rate produces less cracking, but results in a longer processing time. The key to decreasing processing time while simultaneously eliminating shrinkage cracks lies in monitoring the change of the mechanical properties during the evaporation process. Ultrasonic techniques are ideal for this purpose.

To monitor the process, an ultrasonic signal was passed through the material. Spectrum changes were measured and then converted to changes in modulus and viscosity, while shrinkage and density changes were monitored using an air-type transducer and an electronic balance. The results show no observable change up to the beginning of the gelation process, followed by rapid increase in the modulus and viscosity after the onset of shrinkage. This finding was confirmed using a viscometer and laser light scattering measurements. Because of the effectiveness of this ultrasonic technique in detecting changes in the material, such as the onset of cracking, it may be used in controlling and improving the process.

Type
Research Article
Copyright
Copyright © Materials Research Society 1989

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References

1. Prassas, M. and Hench, L. L. “Physical Chemical Factor in Sol-Gel Processing” in Ultrastructure Processing of Ceramics. Glass and Composite, Hench, L.L. and Ulrich, D.R. eds., John Wiley and Sons, N,Y 1984, PP 100125.Google Scholar
2. Hench, L. L., Wang, S. H., and Park, S. C. “SiO2 Gel Glasses”, SPIE'S 28th Annual International Technical Synpoium on optical and Eletrooptics Aug., pp 1924, 1984, San Diego, California.Google Scholar
3. Scherer, G. W.Drying Gel 1. General Theory”, Journal of Non-Crystalline Solids, 87, 1986, PP 199225.CrossRefGoogle Scholar
4. Scherer, G. W.Drying Gel 2. Film and Plate”, Journal of Non-Crystalline solids, 89, 1987, pp 217238.CrossRefGoogle Scholar
5. Brinker, C. J., Keefer, K. D., Schaefer, D. W., Assink, R. A., Kay, B. D. and Ashley, C. S., “Sol-Gel Transition in Sinple silicates II”, Journal of Non-Crystalline solids, 63, 1984, pp 4559.CrossRefGoogle Scholar
6. Hunt, A. J. and Berdahl, P “Structure Data from Light Scattering studies of aerogel” in Better Ceramics Through Chemsity, Brinker, C. J., Clark, D. E., Ulrich, D. R. eds, 1984, pp275280.CrossRefGoogle Scholar
7. Sacks, Michael D. and Sheu, Rong-Shenq “Rhelogical Characterization during Sol/Gel Transition”, in Science of Ceramic ChemiMcal Processing, Hemch, L. L. and Ulrich, D. R. eds, 1986, pp 100107.Google Scholar
8. Hahn, H. T., “Application of Ultrasonic Technique to Cure Characterization of Epoxies”, in Nondestructive Method for Material Property Determnation, Ruud, C. O. and Green, R. E. Jr., 1984, pp 315326.CrossRefGoogle Scholar
9. Tuegel, E. J. and Hahn, H. T. “Ultrasonic Cure Characterization of Epoxy Resins: Constitutive Modeling”, October, 1986, report for Office of Naval Research.Google Scholar
10. Litovitz, T. A. and David, C. M. “Structural and Shear Relaxationin Liquid” in Physical Acoustic IIA by Warren Mason, P., 1969, pp 281349.CrossRefGoogle Scholar
11. Lindrose, A. M., “Ultrasonic Wave and Moduli Chgange in a Curing Epoxy Resin”, Experimental Mechanics, Vol.18, 1978, pp 227232.CrossRefGoogle Scholar