Platinum surface coating and method for manufacturing the same

Abstract

An improved platinum surface coating and method for manufacturing the improved platinum surface coating wherein the platinum surface coating having a fractal surface coating of platinum [“platinum gray”] with a increase in surface area of at least 5 times when compared to shiny platinum of the same geometry and also having improved resistance to physical stress when compared to platinum black having the same surface area. The process of electroplating the surface coating of platinum gray comprising plating at a moderate rate, i.e., at a rate that is faster than the rate necessary to produce shiny platinum and that is less than the rate necessary to produce platinum black.

1 . A platinum surface coating, comprising: 
 a conductive substrate; and a surface coating of platinum having a fractal configuration.    
   
   
       2 . The platinum surface coating of  claim 1  wherein said surface coating has at least  5  times the surface area of that for the corresponding surface area resulting from the basic geometric shape.  
   
   
       3 . The platinum surface coating of  claim 1  wherein said surface coating has a surface area of less than 500 times the corresponding surface area resulting from the basic geometric shape.  
   
   
       4 . The platinum surface coating of  claim 1  wherein said surface coating has a surface area of less than 200 times the corresponding surface are resulting from the basic geometric shape.  
   
   
       5 . The platinum surface coating of  claim 1  wherein said surface coating has a thickness of at least 0.5 microns.  
   
   
       6 . The platinum surface coating of  claim 1  wherein said surface coating has a thickness of at least 5 microns.  
   
   
       7 . The platinum surface coating of  claim 1  wherein said surface coating has a thickness of at least 10 microns.  
   
   
       8 . The platinum surface coating of  claim 1  wherein said surface coating has a thickness of at least 30 microns.  
   
   
       9 . The platinum surface coating of  claim 1  wherein said surface coating has an adhesive strength as measured by critical load greater than 35 millinewtons.  
   
   
       10 . The platinum surface coating of  claim 1  wherein said surface coating appears gray in color.  
   
   
       11 . The platinum surface coating of  claim 1  wherein said surface coating has a lightness (l*) greater than 30 on the CIELAB color scale.  
   
   
       12 . The platinum surface coating of  claim 1  wherein said surface coating has a color density (D) greater than 0.25 D but less than 1.3 D.  
   
   
       13 . The platinum surface coating of  claim 1  wherein said surface coating of platinum comprises alloys of platinum and iridium or rhodium.  
   
   
       14 . The platinum surface coating of  claim 1  wherein said surface coating of platinum comprises alloys of platinum and gold, tantalum, titanium or niobium.  
   
   
       15 . The platinum surface coating of  claim 1  wherein said conductive substrate is platinum, platinum alloy, iridium, iridium oxide or rhodium.  
   
   
       16 . The platinum surface coating of  claim 1  wherein said conductive substrate is gold, tantalum, titanium, titanium nitride or niobium.  
   
   
       17 . A method for electroplating a platinum surface coating having a rough surface, comprising: 
 electroplating the surface of a conductive substrate at a rate such that the particles of platinum form on the conductive substrate faster than necessary to form shiny platinum and slower than necessary to form platinum black.    
   
   
       18 . The method of  claim 17  wherein at least a portion of said rough surface coating has fractal geometry.  
   
   
       19 . The method of  claim 17  wherein said step of electroplating is accomplished at a rate of more than 0.05 microns per minute, but less than 1 micron per minute.  
   
   
       20 . The method of  claim 17  wherein the electroplating process is controlled by electrode voltage.  
   
   
       21 . The method of  claim 20  wherein the voltage is constant voltage.  
   
   
       22 . The method of  claim 20  wherein the controlled voltage causes at least a partially diffusion-limited plating reaction.  
   
   
       23 . The method of  claim 17  wherein the electroplating is accomplished at a rate of more than 0.05 microns per minute, but less than 1 micron per minute.  
   
   
       24 . The method of  claim 17  wherein the voltage of the electroplating process is less than 0.2 Volts and greater than −1 Volts vs. Ag/AgCl Reference electrode.  
   
   
       25 . The method of  claim 17  wherein the voltage of the electroplating process is less than −0.45 Volts and greater than −0.85 Volts vs. Ag/AgCl Reference electrode.  
   
   
       26 . The method of  claim 17  wherein the electroplating solution is at least 3 mM but less than 30 mM ammonium hexachloroplatinate in about 0.4 M disodium hydrogen phosphate.  
   
   
       27 . A platinum surface coating prepared by the method of  claim 17.