GB737373A - Improvements in or relating to the production of porous metallic strip - Google Patents

Abstract

737,373. Coating with metals. BRENNAN, J. B. June 12, 1951, No. 13914/51. Class 82 (2). [Also in Group XXXVI] In a method of making a metallic strip a stream of heated metal particles is sprayed at a constant rate on to a moving base to form a porous layer which is subsequently stripped from the base. The strip has uniform crosssection throughout its length and this is attained by multiple overlapping of sprays or by sequential overlapping of spray from a single spray source. The invention is described with reference to production of porous electrode strips for batteries and electrolytic capacitors. In Fig. 1 electric pump 15 is associated with molten metal 21 in crucible 1 through terminals 11 on conductors 12 and if molten metal 21 falls away from top terminal 11 electric pump 15 operates ram 16 in hydraulic chamber 14 to elevate molten metal 21 whose head is thus kept constant with reference to spray nozzle 8. The molten metal 21 heated by high-frequency coils 2 traverses conduit 6 and atomized by gaseous blast 9 in nozzle 8 is sprayed on to moving base 17 which may consist of aluminium strip or wire cloth anodized by bath 20 or coated by bath 20 with boric acid to facilitate stripping of deposited metal particles 24. The nozzle 8 may comprise fine orifices on the tapered part 6a or several nozzles 8 may be positioned so that sprays overlap. The deposit is uniform in thickness throughout base 17. It is stated that during a given time interval required for the deposit of a particle the movement of the base must be less than the diameter of a particle to permit the hitting of preceding particles by succeeding particles. Preferably the particles deposited on the base exceed 1000 per linear foot. The moving base 17 unwinds from a drum fluid cooled at 18. The metal strip 24 is stripped without tearing from base 17 and Fig. 2 shows a roll-type capacitor comprising porous electrode strips 24 and porous spacers 23 consisting of preformed dielectric or sprayed-on dielectric such as polythene, polystyrene, nylon, cotton and aluminium oxide, alone or in mixtures applied by overlapping sprays. The terminals 22 can be cut from the composite strip 23, 24. Battery electrodes.-The apparatus of Fig. 1 may be used to produce battery electrodes comprising superposed layers of cadmium and iron or zinc and cadmium. A negative electrode may be made by coating a base with zinc oxide and then successively spray-depositing zinc and nickel ; next the three layers are stripped and the zinc oxide face receives zinc and nickel as before. The resultant composite strip may be incorporated into a saturated zincate solution with a porous nickel electrode impregnated with nickel hydroxide as positive. The zinc negative electrode is enclosed by porous nickel but the latter may if desired receive a spray layer of zinc. The invention may also provide the positive electrode by spraying nickel on to nickel hydroxide. The electrodes may be coated with polystyrene.