| 摘要 |
1457712 Forming ceramic heat exchangers CATERPILLAR TRACTOR CO 17 April 1975 [1 Aug 1974] 15911/75 Heading B5A [Also in Division C7] A method of forming an article having passageways e.g. a cross-flow, heat exchanger (see Fig. 1, not shown) comprises assembling together a plurality of walls 32, 36 of a weak and bondable material and a plurality of disintegratable wall support elements e.g. 38 to form a substantially solid body (see lower half of Fig. 2), heating the body to harden and bond the walls 32, 36 together and disintergrating the elements 38 to allow removal from the body to form passageways between the walls 32, 36. The walls 32, 36 may be 15 thou thick and formed from a green ceramic mixture e.g. carbides, oxides or nitrides of beryllium, boron, magnesium, aluminium, silicon, titanium, chromium, zirconium, niobium, hafnium, tantalum and tungsten having ethylene propylene rubber (E.P.D.M.) and magnesium oxide binders. The wall support elements 38 may be formed of a mixture comprising carbon, graphite or boron nitride and E.P.D.M. The amount of E.P.D.M. in the above mixtures may be 45%. The walls 32, 36 and elements 38 may be formed by calendering and cutting. The solid body may be hot pressed initially at 1200‹ F. and 500 p.s.i. in a graphite mould and subsequently at between 2500 and 2950‹ F. and between 2000 and 2500 p.s.i. in an inert or reduring atmosphere. A lubricating layer having a 20 thou thickness and formed of the above wall element material may be applied to the solid body prior to hot pressing. The walls 32, 36 and elements 38 may be coated with a rubber adhesive to reduce relative movement during handling of the solid body. The elements 38, partially disintergrated by the hot pressing, may be removed by further heating in air and/or ultrasonic washing or by chemical action. The density of the fired walls 32, 36 is at least 95%. |
