Properties of Micro & Nanoscopic Particles

The abrasives industry is a many faceted animal.  The technology of creating particles used in polishing hard surfaces has advanced tremendously over the last several decades.  Currently we can manufacture particles measured not just in microns but in nanometers.  A single nanometer is a thousand times smaller than a micron.  The average sized micro-pore of a glass surface is five microns across.  So a ten nanometer particle would be five hundred times smaller than this.  More than size we must consider hardness.  There is also morphology (shape) which is typically controlled by the crystal structure.  Which in turn is controlled by the chemistry.  The property of agglomeration is something to consider as well.  This simply means that the individual particles tend to ‘ball up’.  Such larger agglomerates can create scratches.  Then there is the purity rating.  Powders rated  99.9 percent pure are not at all uncommon.  Next to be considered is the friability of the particle.  In other words, will the particle break up when put to work?  If it does at what pressure and to what size?  This is a very useful property since it allows the user to remove much surface initially then finish with a much smoother surface.  It is also true that friable particles will have new edges for better cutting and refinishing.  There is also the property of chemical reactivity which requires a knowledge of what type of surface the powders will be used on.  Even if the particles will not react directly with the surface forming covalent or even trivalent bonds; they still could be adsorbed onto the surface ionically.  In other words they could be affected by what is otherwise called hydrogen bonding.  One more question to be answered is have these particles been functionalized?  That is has some chemical or chemicals been reacted with the outer surface of the particles so that they are now much more water miscible or oleophilic?  As you can see there is much to consider when looking for a particular particle for a certain formulation or product.  This is a new kind of “particle zoo”!  Lets first consider polycrystalline synthetic diamond particles.  Soda lime flat glass surfaces are rather soft compared to diamond.  Everyone knows that diamond cuts glass.  Just look at how sharp those particles in the above picture are!  Since diamond has a mohs hardness of nine compared to that of glass (which is only seven), you can see how effective these particles  are in resurfacing windows.                                       

There are other abrasives out there too.  Such as cerium oxide, silica, aluminum oxide, silicon carbide, cubic boron nitride, and many more.  All of these posses many different properties.  So there are literally thousands of different abrasives that someone can choose from.  Product development can be rather time consuming because of all the experiments that must be run.  Which includes field testing.  Let me give you an example.

Early on I began experimenting with removing hard water spots from windows using many different abrasives.  I learned real fast that particles  must be at least as hard as glass.  They have to be under five microns in size with a purity rating of 99.9 percent.  No agglomerates.  Also certain diamond abrasives didn’t work any better than other abrasives when used in a paste or slurry.  At least on mineral deposits from concrete and hard water.  Yet there were other stains such as those formed from solutions of sodium metasilicate and sodium carbonate that would only yield to diamond compound and paper towels by hand.  

Written By Henry Grover Jr.

For these posts to appear automatically in your inbox just type your email in the box at the top right "Follow By Email".

For product sales henrygroverjr@gmail.com