Ternary packing of SiC and diamond particles in ethanol
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Ternary packing of SiC and diamond particles in ethanol Jong-Heon Lee, W. Jack Lackey, and James F. Benzel Georgia Institute of Technology, Atlanta, Georgia 30332 (Received 14 October 1994; accepted 10 June 1996)
Particle packing techniques employing a liquid phase were used for preparation of dense disks of SiC and diamond particulates. Forty-one SiC and fifteen diamond compositions in the ternary-component particle systems were used to determine the optimum percentages of coarse, medium, and fine particles for achieving high packing densities: over 80% for SiC and over 62% for diamond. High packing densities were achieved without vibration by simply mixing the three size fractions in ethanol followed by stirring during the initial evaporation stage. The packing density results for SiC were successfully correlated with the percentages of the coarse and fine particles using multiple regression analysis; however, the data for diamond could not be similarly correlated with particle composition because the experimental work was done in a narrow range of compositions and the range of packing densities was small.
I. INTRODUCTION
Most ceramic fabrication processes rely on the initial packing of particles to high density. These include the pressing of particulates prior to sintering,1,2 the packing of nuclear fuel particles into fuel rods,3–7 and the preparation of particulate performs that are subsequently consolidated by the addition of a matrix material via a liquid or gaseous infiltration process.8 Usually it is desired to pack the particles to the maximum density attainable. To achieve high packing density, vibration is normally employed, often over a range of frequencies as high as 4000 Hz and levels of acceleration as high as 20,000 g.3–7,9,10 Numerous other particle packing studies have been reported, often with considerable emphasis having been given to modeling.11–25 The particle size distribution may be discrete or continuous. Both the particle size distribution and particle shape strongly influence the density of the packed bed. Often three rather distinct size fractions are employed.7,23–25 In this case, the percentages of coarse, medium, and fine particles are key variables in achieving high packing density. Typically, a liquid phase is not used. The different size particles may be premixed prior to vibratory packing or the coarse bed may be infiltrated with smaller particles during vibration. Generally, the particle sizes involved have been large, sometimes the larger particles approaching ,1 cm or more in diameter. Both packing theories and experimental results for ternary particle systems show that the size of the particles for the three size fractions should be significantly different in order to achieve efficient packing. The diameter ratios for adjacent size fractions, for example coarse-to-medium, are often ten or more. Packing efficiency decreases rapidly when the size ratio is below seven.18 Often, spherical particles have been used.5–7,10,18 Ternary s
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