The Science of What We Do
Commonly referred to as HPPD, hypersonic plasma
particle deposition is a process has allowed Rushford Hypersonic to begin
leading the way in the deposition coating field of today. With follow on
chemical vapor deposition (CVD), we are opening new dimensions in nanophase
The process and equipment themselves were developed at the University of
Minnesota Institute of Technology's Mechanical Engineering department. The
process itself starts in our patented nozzle, in which particles are dissassociated and then nucleate, forming
a spray that embeds nanoparticles into substrate materials at a very high rate
of speed (~2,400 m/s) with grain sizes in the range of 4-40
nanometers. This thin-film coating violates what is known as the Hall-Petch
Relationship, which states that as grain size decreases, fracture toughness decreases while
hardness increases. For HPPD coatings, as the grain size decreases there is seen a significant increase in BOTH hardness and fracture toughness.
The HPPD process has undergone in-depth testing and characterization at the
University of Minnesota, which found "...as grain size approaches sub 100
nanometer particle size with follow on CVD, fracture toughness increases."
"A nanoparticle containing some 30,000 silicon atoms and moving at 900 meters
per second will bounce off a surface, but at 2000 meters per second, it sticks,
according to computer simulations. The higher-speed impact causes two
sequential changes in the crystalline structure." T. Dumitrica & M. Suri.
University of MN, Phys. Rev. B 78.(2008)
But the most important part of what happens is the nanoparticle that is
now stuck to the material it coated undergoes a phase transition in which, upon
impact during its compressed state, each individual atom bonds to six
neighbors. This allows for the coating to be flexible, with the ability
to be potentially the hardest coating in the market.