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Abstract

An environmentally compliant triboelectric applicator and process for coating or ablating a substrate and for retrieving excess or ejected material from the substrate. The applicator comprises an inner supersonic nozzle for accelerating triboelectrically charged projectile particles entrained in a supersonic gas to speeds sufficiently high to coat or ablate a substrate. The applicator further comprises an outer evacuator nozzle coaxially surrounding the inner supersonic nozzle for retrieving excess projectile particles, ablated substrate powders, or other environmentally hazardous materials. A fluid dynamic coupling uses the efficacy of the Mach turning angle associated with a supersonic boundary layer of carrier gas to aspirate the central core of the supersonic two-phase jet. This fluid coupling and spacing between the outlet of the supersonic nozzle and the substrate also permits the substrate to triboelectrically charge to levels which induce electrostatic discharges at the substrate simultaneous to the impacts. The aspiration feature reduces the outlet pressure in the central core of the nozzle below ambient pressure which allows the projectiles to travel unimpeded to the substrate, and reduces the inlet pressure required to achieve parallel and shock-free flow with the inner supersonic nozzle. The powders are injected into the carrier gas using powder feeders modified for high pressure and the ablated debris with excess projectile particles are collected in a particle precipitator and filter unit using a suction blower. A special nozzle applicator embodiment and process for coating or ablating the internal surface of a cylinder bore is also disclosed. This nozzle applicator comprises an axisymmetric cylindrical nozzle for conveying, accelerating, and triboelectrically charging projectile particles entrained in a carrier gas to speeds sufficiently high to coat or ablate the internal surface of the cylinder bore substrate when impacted by a triboelectrically charged jet comprising a central core.

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First Claim