Further considerations on the preparation of small electrical contacts by spot welding

A recent publication by the authors describes a spot welder which can be us ed to join small wires to samples of metallic materials. The article also d iscusses the selection of contact wires, the preparation of samples prior t o welding, and other details of the welding method. In the present work, we give a much improved version of the power supply circuit, and offer additi onal information on the technique that was not discussed previously. A "uni versal" method of electropolishing is also described which may be used to r emove oxides and other surface contaminants from samples prior to spot weld ing. This technique can be applied to a variety of materials, including rar e earth elements and compounds, which are generally difficult to polish or etch using other chemical or electrochemical means. (C) 2000 American Insti tute of Physics. [S0034-6748(00)04805-X].