FIB preparation of a sensitive porous catalyst for TEM elemental mapping at high magnifications

Doped skeletal copper catalysts, created by selective dissolution of aluminium from a copper-aluminium alloy by caustic in the presence of an additive, has been imaged at very high magnification using a TEM. The location of the additive species has been determined by elemental mapping using an attached EDS detector. Zinc resides primarily inside the copper ligaments while chromium resides on the outside of the ligaments. Since skeletal copper is highly porous and extremely sensitive, conventional TEM preparation techniques could not be used. The preparation of the TEM samples was carried out using a focussed ion beam (FIB) miller. Several methods are outlined, along with the reasons some of them were unsuccessful for this particular material. The successful result indicates this technique may be used to analyse similar skeletal materials, such as nickel, cobalt, etc., which are otherwise difficult to prepare. It may also provide a basis for high resolution imaging or elemental analysis of other porous and/or highly sensitive materials. (C) 2001 Kluwer Academic Publishers.