Layered Emitter Coating Structure for Crack Resistance with PDAG Coatings

Abstract

A thermal management apparatus includes an electrohydrodynamic fluid accelerator in which an emitter electrode and another electrode are energizable to motivate fluid flow. The emitter electrode is a layered structure including an electrode core material and an outermost coating that is susceptible to micro-cracking or corona erosion. A barrier material is provided in a sublayer to protect the underlying electrode core material. An adhesion promoting layer may be used between the barrier material and the electrode core material or between other layers of the structure. solid solution. A method of making an EHD product includes positioning the layered electrode relative to another electrode to motivate fluid flow when energized.

1 . A multi-layered electrode for use in an electrohydrodynamic device, the electrode comprising:
 an electrode core material;   a coating about the core material, the coating being susceptible to compromise due to adverse effects from a plasma discharge environment; and   a barrier material between the electrode core material and the coating, the barrier material selected to substantially mitigate exposure of the electrode core material to the plasma discharge environment following compromise of the coating.   
     
     
         2 . The electrode of  claim 1 , wherein the barrier layer is selected to resist the adverse effects from a plasma discharge environment following at least one of micro-crack formation, pinhole formation, defect formation, erosion and consumption of a portion of the coating. 
     
     
         3 . The electrode of  claim 1 , wherein the coating is a solid solution comprising a solvent metal and at least one solute material. 
     
     
         4 . The electrode of  claim 3 , wherein the barrier material includes a diffusion barrier material selected to bound diffusion of the solute material within the solvent metal. 
     
     
         5 . The electrode of  claim 1 , further comprising an adhesion promoting layer between the barrier material and at least one of the electrode core material and the solid solution coating. 
     
     
         6 . The electrode of  claim 5 , wherein at least one of the barrier material and the adhesion promoting layer comprises at least one of nickel, gold, titanium-tungsten alloy, chromium, rhodium, iridium, platinum and palladium. 
     
     
         7 . The electrode of  claim 5 , wherein at least one of the barrier material and the adhesion promoting material further comprises multiple distinct layers. 
     
     
         8 . The electrode of  claim 7 , wherein the multiple layers of the at least one of the barrier material and the adhesion promoting material include nickel, rhodium, iridium, platinum, palladium, gold, titanium-tungsten alloy and chromium. 
     
     
         9 . The electrode of  claim 1 , wherein the coating comprises a solid solution in which a solvent metal includes palladium and a first solute material includes silver. 
     
     
         10 . The electrode of  claim 1 , wherein the electrode core material comprises at least one of tungsten, titanium, steel, tantalum, molybdenum and nickel. 
     
     
         11 . The electrode of  claim 1 , wherein the coating is a solid solution formed by heat treating distinct solvent metal and solute material depositions. 
     
     
         12 . The electrode of  claim 1 , wherein the coating comprises an ozone reducing material. 
     
     
         13 . A method of forming an electrode, the method comprising:
 providing an electrode core material;   providing a coating over the electrode core material, the coating being susceptible to compromise due to adverse effects from a plasma discharge environment; and   providing a barrier material between the electrode core material and the coating to substantially mitigate exposure of the electrode core material to the plasma discharge environment following compromise of the coating.   
     
     
         14 . The method of  claim 13 , further comprising providing an adhesion promoting material between the barrier material and at least one of the electrode core material and the coating. 
     
     
         15 . The method of  claim 13 , wherein at least one of the adhesion promoting material and the barrier material comprises nickel. 
     
     
         16 . The method of  claim 13 , wherein providing the coating includes heat treating silver and palladium deposits such that the silver diffuses into the palladium but not into the barrier material. 
     
     
         17 . The method of  claim 13 , further comprising providing a Pt group metal layer between the electrode core material and the coating. 
     
     
         18 . An electrohydrodynamic device comprising:
 one or more collector electrodes; and   a layered emitter electrode in spaced relation to the one or more collector electrodes; the layered emitter electrode and one or more collector electrodes being energizable to motivate fluid flow along a flow path;   wherein the layered emitter electrodes comprises:
 an electrode core material; 
 a coating about the core material, the coating being susceptible to compromise due to adverse effects from a plasma discharge environment; and 
 a barrier material between the electrode core material and the coating, the barrier material selected to substantially mitigate exposure of the electrode core material to the plasma discharge environment following compromise of the coating. 
   
     
     
         19 . The device of  claim 18 , wherein the coating comprises a solid solution of a solvent metal and a solute material, the solute material exhibiting one or more of ozone reactivity, resistance to oxidation, resistance to corona erosion, low coefficient of friction, and low surface adhesion. 
     
     
         20 . The device of  claim 18 , wherein the coating comprising palladium and nickel, the layered electrode further comprising an adhesion promoting layer comprising nickel between the electrode core material and the coating. 
     
     
         21 . An apparatus comprising:
 an enclosure; and   a thermal management assembly for use in convection cooling of one or more devices within the enclosure, the thermal management assembly defining a flow path for conveyance of air between portions of the enclosure over heat transfer surfaces positioned along the flow path to dissipate heat generated by the one or more devices, the thermal management assembly including an electrohydrodynamic (EHD) fluid accelerator comprising:   one or more collector electrodes; and   a layered emitter electrode in spaced relation to the one or more collector electrodes; the layered emitter electrode and one or more collector electrodes being energizable to motivate fluid flow along a flow path;   wherein the layered emitter electrodes comprises:
 an electrode core material; 
 a coating about the core material, the coating being susceptible to at least one of micro-cracking, pin hole formation, coating defect formation and corona erosion; and 
 a barrier material between the electrode core material and the coating, the barrier material selected to substantially mitigate exposure of the electrode core material to the plasma discharge environment following compromise of the coating. 
   
     
     
         22 . The apparatus of  claim 21 , wherein the one or more devices includes one of a computing device, laptop computer, tablet computer, smart phone, projector, copy machine, fax machine, printer, radio, audio or video recording device, audio or video playback device, communications device, charging device, power inverter, light source, medical device, home appliance, power tool, toy, game console, television, and video display device.