Graphite mouldings contg. fine metal powder - with optimum electrical conductivity and abrasion resistance, suitable for brushes

摘要

Electrically conducting mouldings with isotropic properties are made from graphite and =1 other conducting material. Graphite powder with grain size 400 mu is suspended in a carrier in which a carbonisable binder is also dissolved or dispersed; the suspension is spray dried to obtain spheroids, fed into a fluisided bed drier for coating with at least one layer of conducting material. The conducting material is suspended in a carrier contg. a carbonisable binder in soln. or dispersion, where 0.1-20% binder is used w.r.t. the conducting material, the suspension being fed into the drier. The coated and dried graphite spheroids are pressed into mouldings and subjected to heat treatment. The mouldings are used for electric contacts, e.g. Cu brushes contg. a large amt. of graphite and used in motors for domestic appliances, razors, or starter motors. As compared with conventional brushes, the graphite content is higher so abrasion resistance is better, but good electrical conductivity is attained, even with only 40% Cu. Silver can be used instead of Cu, and also other metals, e.g. Fe, Co, Ni, Au, Al.