Preparation of Particulates for Transmission Electron Microscopy: An Update
A method for preparing fragmented or particulate ceramic materials for transmission electron microscopy (TEM) by embedding in a solid metal matrix such as aluminum, using vacuum hot-pressing at about 550°C, followed by mechanical thinning and ion milling, has been published. This technique is useful for most high-melting ceramic materials but may introduce thermal damage to low-melting materials or to hydrated minerals. We describe here two relatively simple techniques that can be carried out at room temperature and that do not require vacuum hot-pressing equipment.The first technique disperses the sample in a dental amalgam. Premeasured capsules contain the silver alloy powder and mercury in separate compartments. The capsule is opened and a small amount of sample is added. The capsule is then closed and compressed to release the mercury and agitated for 1 to 2 min. The material is removed from the capsule and tightly packed into a 3-mm-diam cylindrical mold for hardening overnight. The resulting pellet is then sliced and thinned as in the earlier method. Figure 1 shows a coal fly ash particle prepared by this technique.