Microstructure and microchemistry of silicon particles formed during electrical-discharge machining

Abstract

The structure and morphology of particles representing the byproduct of electrical-discharge machining (EDM) were analyzed using transmission electron microscopy (TEM). The EDM process involved high-efficiency and high-accuracy fine boring of a single-crystal silicon ingot by high-frequency electrical spark discharges. As the silver electrode advanced, spark-discharge-melted or vaporized small particles of the silicon workpiece were produced and the particles were flushed away and collected in deionized water. Standard TEM and analytical electron microscopy (AEM) observations were carried out. Bright-field (BF) images, diffraction, and energy-dispersive X-ray spectrometry (EDXS) data were obtained to completely characterize the EDM particles. BF images indicated the presence of large silicon particles decorated by smaller silver particles originating from the electrode as the byproducts of the EDM processing. Analysis of the particle-size distribution resulted in an average silicon particle size of about 500 nm decorated by smaller silver particles of an average size of about 65 nm. EDXS spectra depicted individual silicon and silver particles with characteristic peaks that identify the elements present. Selected-area electron diffraction (SAED) pattern confirmed the presence of crystalline silicon. Finally, a set of SAED patterns, EDXS profiles, and TEM images is included that fully describe the particles' chemistry, structure, and morphology, respectively.