RF atmospheric plasma systems for deposition of nanostructures

Summary form only given. Two types of RF atmospheric plasma systems were used for deposition of nanostructures on polymer substrates. Both systems consist of the quartz tubes equipped by the RF antennas at frequencies 13.56 MHz and/or 27.12 MHz and a Laval nozzle at the end. The nozzle provides simultaneously nucleation of the nanoparticles in the fly, accelerates them in the direction of the substrate and keeps the nanoparticle flow at the outlet cold enough to protect the polymer substrate from thermal damages. Both systems have a two-stage design where the first stage serves as a generator of the droplets of the melted precursor as well as a trigger and sustainer of the ICP plasma in the second stage that is in reality a RF plasma chemical reactor with feeding of processing gases. In the first type a DC plasma torch with hollow hafnium cathode for an axial feeding of the precursors with feeding rate up to 1 kg/h was used. The droplets undergo a series of plasmochemical reactions in the RF reactor, where all of them are converted in an axial vapor flow. To increase the dwelling time the reactor consists of 12" long quartz tube with 4.5" OD and is supplied by two RF coils. The bottom coil is connected to the 13.56 MHz generator and the top to the 27.12 MHz one. The second type served for deposition of ultra-high purity materials. The DC plasma torch was replaced by a commercial ICP-OES torch that provides relatively low velocity of the flow and the droplets have enough dwelling time in the second stage to be evaporated. Therefore, the length of the RF reactor was reduced twice. The second stage has one saddle-like RF antenna that concentrates all RF power in the gap between its right and left parts. Each part serves also as a capacitor\´s plate and creates first a capacitively coupled discharge before the development of an ICP one. The speed of the vapor flow at the exit of the reactor is relatively low. So, the conditions for nucleation of nanoparticles in the La- al nozzle are completely different comparing with the DC-RF-RF plasma system. The use of Laval nozzle with special profile increases the flexibility of the control of ICP plasma spraying for producing of nanostructured coatings under atmospheric conditions. Estimation of the ICP plasma parameters and the cooling time in the Laval nozzle are presented