to heat treatment per step 5 which includes removing the binder i e debinding and removing the filler material as well as sintering of the remaining multi channel green body structure comprised of the channeled structural material the selection of the filler to a great degree is dependent on the type of structural materials in that the filler should remain in place until sufficient mechanical integrity develops in structural material but it should be removed under conditions that do not deteriorate the properties of the structural materials in addition the filler material should be chemically compatible with the structural material over the temperature range both in existence filler that remains to relatively high temperature before it is removed will have a wide range of applicability to a variety of structural materials for example mgo cao etc will not be removed during the process of sintering they allow for the holding of the shape of the channels during sintering and they can be removed by dissolution after sintering accordingly they could be used as fillers for high temperature refractory metals such as w ta and the like when the development of sufficient structural integrity of the shell require temperatures as high as 800 u00b0 to 1200 u00b0 c clearly filler material should not form new undesirable compounds with the structural material if low temperature polymer is used which is removed before structural materials develop sufficient mechanical integrity the multi channel structure could be unstable and collapse it is possible to use lower melting temperature filler but in that case the filler removal should be conducted very slowly in the powder bed to support the structure the chemical composition of the channeled structural materials will typically be that of the starting structural.