Title of Invention

FIBRE NICKEL MAT SUBSTRATES FOR NI/CD BATTERIES

Abstract

A method of manufacture of a fibre nickel mat substrate comprising the steps of sensitising a polymeric fibre mat with an acidic solution of stannous chloride; Washing the sensitised mat with de-ionised water until pH of the said mat is 6 to 8; activating the sensitised mat with an acidic solution of palladium chloride; washing the activated mat with de-ionised water; electroless copper plating the activated mat; washing the copper plated mat with de-ionised water until the pH of the drip water is 6; electro-nickel plating the copper plated mat; washing the nickel plated mat with de-ionised water and drying the same; pyrolysing the nickel plated mat in open atm osphere and sintering the same therafter to obtain a fibre nickel mat having a dense network of nickel filam ent with a large number of sintered joints and high porosity, together with high conductivity and mechanical strength.

Full Text

This invention relates to a method of manufacture as detailed in "Process Flow Diagram" (Fig. 1) of a fibre nickel mat for use as substrate in the manufacture of nickel and cadmium electrodes and a fibre nickel mat substrate manufactured by the said process towards nickel cadmium cell / battery requirement, as shown in representative figure (Fig.2). In the manufacture of nickel cadmium batteries, pocket plates have been initially used in the fabrication of the electrodes. During fabrication of the electrodes, the active material is placed (or filled) inside small pockets. A single electrode would have many of such pockets welded together with supporting perforated metal strips. Later, sintered plate technology has been developed, in order to increase the quantity of active material in an electrode for the purpose of increasing the capacity of a cell. In this system, a nickel or nickel plated steel material is coated with nickel oxide along with bonding agents and the coated material is then sintered in an inert material. The sintered material thus prepared has 80% porosity. The plates are then filled with active material either by chemical or by electro-chemical impregnation methods. i In sintered technology, porosity can be achieved to around 80% and any further increase in porosity weakens the structural rigidity of the material. In this invention however the porosity of the substrate is further increased without sacrificing the structural rigidity of the substrate. The method, according to this invention, comprises the steps of sensitising a polymeric fibre mat with an acidic solution of stannous chloride; washing the sensitised mat with de-ionised water until the pH of the said mat is 6 to 8; activating the sensitised mat with an acidic aqueous solution of palladium chloride; washing the activated mat with de-ionised water; electrodes copper plating the activated mat; washing the copper plated mat with de-ionised water until the pH of the drip water is 6; electro nickel plating the copper plated mat; washing the nickel plated mat with deionizer water and drying the same; paralyzing the nickel plated mat in open atmosphere and sintering the same in a reducing atmosphere thereafter to ; obtain a fibre nickel mat having a dense network of nickel filament with a large number of sintered joints and high porosity, together with high conductivity and mechanical strength. EXAMPLE A polymeric fibre mat (such as polyolefin) is cut to the required size. The cut fibre mat is 2. " sensitised with an aqueous solution of stannous chloride of 2 to 8 % w/v concentration acidified by HC1 of5tol5% v/v concentration. The sensitising overheat is carried out for 5 to 20 minutes. The sensitised mat is then washed with de-ionised water until the pH of the said mat is 6 to 8. The sensitised mat is then activated by an aqueous solution of palladium chloride of ,^ concentration 0.2 to 1.0% w/v acidified by HC1 of concentration 0.2 to 1% v/v . The activation is done by soaking the mat in the said acidified solution of palladium chloride. The activation of the mat is carried out for 5 to 20 minutes. Air entrapped inside the mat is removed by shaking die same in air. " The activated mat is then washed with de-ionised water to neutral pH. The activated mat is then electro less copper plated and washed with de-ionised water until the pH of the drip water is neutral. The mat is thereafter electro-nickel plated and then washed with de-ionised water to neutral pH and dried. The nickel plated mat is then paralyzed in open atmosphere and sintered in a reducing atmosphere (800 to 1100 degree C) to obtain a fibre nickel mat having a dense network of nickel film ent with a large number of sintered joints and high porosity. The mat also exhibits high electrical conductivity and mechanical strength. The terms and expressions herein are of description and do not limit the scope and ambit of this invention. We Claim: 1. A method of manufacture of a fibre nickel mat substrate comprising the steps of sensitising a polymeric fibre mat with an acidic solution of stannous chloride; washing the sensitised mat with de-ionised water until pH of the said mat is 6 to 8; activating the sensitised mat with an acidic aqueous solution of palladium chloride; washing the activated mat with de-ionised water; electroless copper plating the activated mat; washing the copper plated mat with de-ionised water until the pH of the drip water is 6; electro-nickel plating the copper plated mat; washing the nickel plated mat with , de-ionised water and drying the same; pyrolysing the nickel plated mat in open atmosphere and sintering the same thereafter to obtain a fibre nickel mat having a dense network of nickel filament with a large number of sintered joints and high porosity, together with high conductivity and mechanical strength. 2. A method as claimed in Claim 1 wherein the said mat is cut to the desired size before sensitising. 3. A method as claimed in Claim 1 or Claim 2 wherein the said mat is sensitised by soaking the same in aqueous stannous chloride solution of 2 to 8 % w/v concentration acidified by HC1 of 5 to 15 % v/v concentration. 4. A method as claimed in any one of the preceding Claims wherein the sensitising of the said mat is carried out for 5 to 20 minutes. 5. A method as claimed in any one of the preceding Claims wherein the sensitised mat is activated by soaking the same in the said aqueous palladium chloride solution of 0.2 % to 1% w/v concentration acidified by HC1 0.2 to 1 % v/v. wherein the activation of the said mat is carried out for 5 to 20 m inutes. 7. A method as claimed in any one of the preceding Claims wherein the air trapped inside the mat is removed by shaking the same in air. 8.A method of manufacture of a fibre nickel mat substrate for a nickel cadmium battery substantially as herein described. 9. A fibre nickel mat substrate for a nickel cadmium battery whenever manufactured by a method in accordance with any one of the preceding Claims. 10.A fibre nickel mat substrate for a nickel cadmium battery comprising a polymeric fibre mat sensitised and activated by acidic aqueous solutions of stannous chloride and palladium chloride, said mat being electro less copper plated, electro-nickel plated, pyrolysed and sintered. 11. A fibre nickel mat substrate for a nickel cadmium battery substantially as herein described.

Documents:

0242-mas-2001-abstract.pdf

0242-mas-2001-claims-duplicate.pdf

0242-mas-2001-claims.pdf

0242-mas-2001-corespondence-others.pdf

0242-mas-2001-corespondence-po.pdf

0242-mas-2001-description-(complete)-duplicate.pdf

0242-mas-2001-description-(complete).pdf

0242-mas-2001-drawings.pdf

0242-mas-2001-form-19.pdf

0242-mas-2001-form-26.pdf

0242-mas-2001-form-4.pdf