Article including particles oriented generally along an article surface and method for making

Abstract

Non-spherical particles including a major dimension, for example flakes of material, are positioned with the major dimension oriented generally along an article surface in respect to which the particle is disposed. The particles, disposed in a fluid medium, the viscosity of which can be increased to secure the particles in position, are positioned using a force on the particles. The force includes torque force from a magnetic field, force from flow of the fluid medium, the force of gravity, and the force of surface tension alone or in combination with the force of gravity.

What is claimed is:  
     
         1 . An article including a non-planar article surface and a coating on the article surface comprising a plurality of non-spherical particles each having a major dimension, an average of at least about 50% of the major dimensions being oriented generally along the article surface in respect to which the particle is disposed.  
     
     
         2 . The article of  claim 1  in which the particles are disposed in a coating on the article surface, the coating comprising a matrix about the particles.  
     
     
         3 . The article of  claim 2  in which: 
 the article surface is of a complex, three dimensional non-planar shape;  
 the matrix is non-metallic; and,  
 the coating comprises metallic flakes having an aspect ratio in the range of about 10-100 in the non-metallic matrix.  
 
     
     
         4 . The article of  claim 3  in the form of a component of a power generating apparatus.  
     
     
         5 . The article of  claim 3  in the form of a component of a vehicle.  
     
     
         6 . The article of  claim 3  in which the metallic flakes have an aspect ratio in the range of about 15-30.  
     
     
         7 . The article of  claim 3  in which the metallic flakes are magnetic.  
     
     
         8 . A method using a magnetic field to orient with respect to an article surface a plurality of non-spherical particles each including a major dimension and each of which can be moved by a force applied to each particle, the particles being of a material which will react with a magnetic field, the particles being disposed in a fluid medium which will not react to a magnetic field and the viscosity of which can be increased, comprising the steps of: 
 providing substantially parallel relative movement between the magnetic field, and each particle and the article surface in respect to which each particle is disposed, while    disposing the magnetic field with its direction relative to the article surface so that, during the relative movement, the magnetic field will locate an average of at least about 50% of the major dimensions in a position generally along the article surface in respect to which each particle is disposed, as each particle passes through the magnetic field; and,    increasing the viscosity of the medium to secure each particle in the position.    
     
     
         9 . The method of  claim 8  in which: 
 the magnetic field is provided by disposing a magnet with a centerline of its N-S poles within about 30° of perpendicular to the article surface over which it is disposed and spaced apart from the particles at a distance, the magnet extending the magnetic field around the particles to apply to the particles a torque force capable of moving the particles in the fluid medium; and  
 with the magnet maintained substantially at the distance, providing the relative movement between the magnet and the particles.  
 
     
     
         10 . The method of  claim 9  in which: 
 the article surface is non-planar; and,  
 the magnet is carried at the distance as the relative movement between the magnet and the article surface substantially follows the non-planar article surface.  
 
     
     
         11 . The method of  claim 10  for providing a coating on a complex, three dimensional non-planar surface of a component of a power generating apparatus in which: 
 the magnetic field is in the range of about 100-1000 oersteds;  
 the distance is in the range of about ¼-1.5″;  
 the particles are metallic, magnetic flakes having an aspect ratio in the range of about 10-100; and,  
 the fluid medium includes a curable polymeric material.  
 
     
     
         12 . The method of  claim 1  in which the magnetic flakes are a ferromagnetic material having an aspect ratio in the range of about 15-30.  
     
     
         13 . A method for orienting with respect to an article surface a plurality of non-spherical particles each including a major dimension and each of which can be moved by a force applied to each particle, comprising the steps of: 
 disposing the particles in a fluid medium the viscosity of which can be increased;    applying a force to the medium carrying the particles to flow the medium substantially parallel to the article surface,    the medium applying a force on the particles sufficient to locate an average of at least about 50% of the plurality of particles with the major dimension in a position generally along the article surface in respect to which each particle is disposed; and,    increasing the viscosity of the medium to secure each particle in the position.    
     
     
         14 . An article in the form of a sheet made by the method of  claim 13 .  
     
     
         15 . An article made by the method of  claim 13  comprising an article surface and a coating disposed on the article surface in which: 
 the fluid medium including the particles is disposed on the article surface; and,  
 the force is applied to the medium to locate the particles in the position.  
 
     
     
         16 . A method for orienting with respect to an article surface a plurality of non-spherical particles each including a major dimension and each of which can be moved by a force applied to each particle, comprising the steps of: 
 disposing the particles in a medium the viscosity of which can be increased, the medium being in a fluid condition;    disposing the medium with the particles on the article surface;    locating the article surface substantially perpendicular to a force of gravity;    maintaining the medium in the fluid condition for a time selected to enable the force of gravity to locate an average of at least about 50% of the plurality of particles with the major dimension in a position generally along the article surface in respect to which each particle is disposed; and,    increasing the viscosity of the medium to secure each particle in the position.    
     
     
         17 . A method for orienting with respect to an article surface a plurality of non-spherical particles each including a major dimension and each of which can be moved by a force applied to each particle, comprising the steps of: 
 disposing the particles in a medium the viscosity of which can be increased;    the medium being in a fluid condition with the viscosity selected to provide a selected surface tension in the medium;    disposing the medium with the particles on the article surface; and,    maintaining the medium in the fluid condition for a time selected to enable the surface tension to located at least about 50% of the plurality of particles with the major dimension in a position generally along the article surface in respect to which each particle is disposed.    
     
     
         18 . The method of  claim 17  in which: 
 the medium with the particles is disposed in a coating of a plurality of superimposed layers on an article surface,  
 each layer being maintained in the fluid condition for the time prior to disposition of a subsequent superimposed layer to enable a combination of gravity and surface tension to locate at least about 60% of the plurality of particles in the coating with the major dimension in the position.  
 
     
     
         19 . The method of  claim 18  in which each layer has a thickness in the range of about 0.008-0.012″.