Preparation of Thin-Foil TEM Specimens from Sub-Millimeter Particulate

Abstract

ABSTRACTThe particulate produced by many of the methods of rapid solidification, such as atomized powder, is of order 50 microns in diameter and is thus much too small to form the 3mm diameter disc conventionally used for thin-foil microscopy. 50 microns is, however, much too thick for direct TEM study on a support film and grid. A technique is described in detail that produces a composite wafer where atomized metal powder is sandwiched between two layers of electroplated nickel. This wafer is about 25 mm in diameter and about 250 microns thick. 3mm diameter TEM discs can be punched from the wafer and thinned by combinations of grinding, dimpling, jet-polishing, and ion milling. Depending on the composition and structure of the powder under study, the composite nature of the wafer can sometimes promote undesirable galvanic effects during jet polishing and differential thinning rates during ionmilling. Typical results are presented and discussion of the benefits and shortcomings of this technique is made. The method should be applicable to a variety of materials and geometries.