Particle- and Grain-Size Measurement by X-Ray Fluorescence

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Department of Materials Science and Engineering


A method of particle size measurement is presented which is based on the fact that the intensity of fluorescent X-rays from an element in a particle is dependent on particle size. The effect can be expressed by the intensity ratio R, the ratio of the intensity from a sample containing particles of size S to the intensity from a sample containing particles of zero size, both samples having the same concentration of the fluorescing element.

An equation relating R and S was derived for low concentrations of cubic particles suspended in a matrix material. The equation predicts that R will depend only on the particle size S, the sample thickness, and the linear absorption coefficients of the particle and matrix materials.

Experiments were conducted using closely-sized fractions of W, Cu, and bronze powders in various matrices. It was found that by varying the incident X-rays, the matrix material and the fluorescent X-rays, the sensitivity of R to different ranges of particle size can be controlled. R was found to decrease with particle concentration and small deviations in linearity were found for mixtures of particle sizes. The experimental results were in fair agreement with the equation.

The method is rapid and non-destructive, requires only a small amount of sample and permits measurement of the sizes of different particle species in a single sample. It appears to be particularly attractive for rapid, routine measurements of average particle size on many commercial powders as well as for grain size measurement on alloy and rock samples. It appears possible to use the method for on-stream particle size measurement of suspensions.

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© 1969

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Powder Technology