Abstract: A catalyst unit (16), in which a quantity of a relatively expensive material such as platinum is replaced by a greater quantity of a relatively inexpensive material such as palladium. Thus, material cost saved by "tailoring" a pack is used to pay for a large quantity of a cheaper material. Although the cheaper material is generally less intrinsically efficient than the expensive material, a sufficient additional amount of the cheaper material can be used to more than compensate for this lack of efficiency. Thus, a catalytic pack of high catalytic efficiency, low material cost, low metal loss and long run duration can be produced.

Abstract: This specification describes an igniter, particularly for gas turbine engines, and comprising two or more electrodes separated by a body of insulating or semi-conducting material and having exposed working surfaces between which sparks may pass, at least part of the working surface or surfaces of at least one of the electrodes comprising a host material in which Co or Ni predominates alloyed or compounded with one or more additional metals selected from the group consisting of Ru, Rh, Pd, Ir, Pt, Ag and Au. Preferably, the additional metal is platinum which is present in an amount of 1 to 20 wt.% of the total metal content.