Sizing particles with X-ray sedimentation: despite the emergence of other particle sizing methods over the past several decades, X-ray sedimentation remains the method of choice for many ceramic manufacturers.

An exact method of determining particle size by sedimentation was developed in the 1850s by George Gabriel Stokes, who derived an equation (known as Stokes' law) describing the settling rates of spheres in a fluid as a function of size. Since early in the 20th century, it has been known that the attenuation of X-radiation is proportional to the mass of the absorber. In the mid-'60s, Olivier and Hickin, (1) working in a Freeport Kaolin laboratory, combined these two principles and developed an instrument that uses sedimentation to determine particle size and X-ray absorption to measure the time-dependent change in a mass concentration of solids settling from suspension. The technology was acquired by Micromeritics Instrument Corp. and introduced as a commercial instrument * in 1967. Implementation of the X-ray sedimentation technique for particle sizing has evolved considerably over the years.

Since the introduction of the X-ray sedimentation instrument, a number of other types of analytical instruments have been developed based on different techniques of sizing and quantity determination. Scientists and technologists newly entering the field of particle technology often wonder why X-ray sedimentation continues to be the method of choice in a number of applications. The reasons for remaining with this technique vary from user to user, but two reasons seem to prevail: first, the direct way in which size and quantity are determined, and second, the ability of the user to understand how variations from the theoretical model affect reported results. Because of these advantages, X-ray sedimentation continues to be widely used throughout the ceramic and related industries for accurate particle size analysis.

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