Characteristics On Plasma Synthesis And Combustion Process Research Of Metal Nanoparticles

With the wide application of nano-energetic material in national defense,aerospace and industrial production,the research on its synthesis and combustion mechanism has attracted a great deal of attention.However,mechanisms on the synthesis of nano-metal particles and their combustion characteristics are not well understood.In this paper,nano-metal particles were synthesized by the improved wire electrical explosion method based on inert-gas condensation theory.A flat flame burner has been employed to provide high temperature flue gas,where the combustion characteristics of pure aluminum and titanium particles were studied.First,a high-frequency nanosecond pulse power was designed for the plasma synthesis of nano-metal particles.The power supply consists of rectifier,boost-up,oscillation and other circuits,generating high energy nanosecond pulses with voltage amplitudes of 3000 V.The experimental results show that designed power well meets the requirements for plasma synthesis.Then,nano-sized aluminum and titanium particles were synthesized using the designed nanosecond pulse discharge to ablate the electrodes.The experiments divulge that the particle size and concentration decrease with the increasing velocity of cooling gas and the decreasing discha rge frequency.According to the energy conversion model,20.5% of the power energy converts to the heat for metal electrode ablation.Finally,pure nano-metal particles were brought into high-temperature flue gas and their combustion characteristics were investigated.The results show that aluminum particles cloud with equivalent diameters of 130 nm are oxidized and form a red flame of which the characteristic burning time is about 4.64 ms in the flue gas of 1200 K.Individual emission streaks can be observed during the burning process of titanium particle agglomerates.For titanium agglomerates with mobility equivalent diameters ranging from 70 nm to 100 nm,their burning time does not change significantly with the variation of the equivalent sizes.The Avrami-Erofeev model(A4)has been applied to characterize the mass consumption of titanium particles.Combined with heat transfer model and energy equation,the combustion process of titanium particles is accurately simulated.