Based on the idea that a large number of charged particles can be generated by a high-frequency alternating current (AC) dielectric barrier discharge (DBD), and charged particles can be accelerated directionally by a direct current (DC) electric field, a new type of ionic wind formation method is proposed in this paper. To this end, a carbon fiber spiral electrode serves as the generation electrode and a metal rod electrode as the collection electrode, with AC and DC potentials applied respectively to the generation electrode and the collection electrode to form an AC-DC coupled electric field. Under the action of the coupled electric field, a dielectric barrier discharge is formed on the carbon fiber spiral electrode, and the electrons generated by the discharge move from the generation electrode to the collection electrode in the opposite direction of the electric field vectors. During the movement, energy is transferred to the gas molecules by their colliding with neutral gas molecules, thereby forming a directional gas stream movement, i.e. ionic wind. In the research process, it is verified through electric field simulation analysis and discharge experiment that this method can effectively increase the number of charged particles in the discharge process, and the velocity of the ionic wind is nearly doubled. On this basis, the addition of a third electrode forms a distinct discharge region and an electron acceleration region, which further increases its velocity. The experimental result shows that the ionic wind speed reaches up to 2.98 m s −1 . Thanks to the ability of the electrode structure to generate an atmospheric pressure DBD plasma and form an ionic wind, we can create a noise-free air purification device without resorting to a fan, with this device having good application prospects in the field of air purification.

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The microstructure of a microalloying non-quenching and tempering steel developed recently was analyzed through OM, SEM and TEM, in order to find the strengthening and toughening mechanisms of the steel. All of the dislocations and subgrain boundaries in the grains, the martensite in the martensite-austenite islands of the grainy bainite structure, the dispersed phases in the grains and at the grain boundaries, and the grain size were observed and studied in our experiments. The results indicate that the strengthening results from phase transition, dislocation, subgrain structure, dispersion phase and fined grain, and the toughness relates with the ferrite matrix consisting of the grainy bainite and the grain size of the steel. The mechanisms between the hot-rolled-and-cooled and the tempered steel are slightly different.

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Nanocrystalline diamond matrix (or patterned nanocrystalline diamond) have been grown by hot filament chemical vapor deposition (HFCVD) on copper substrates, which were masked by a copper template filled with through-holes. The influence of the mixing ratio for CH4/H2 source gases, total gas pressure and the aspect ratio (the ratio of hole depth to its diameter) on the morphology, grain size and quality of diamond films were investigated. Continuous diamond films were obtained under 2.0 kpa. When increasing the aspect ratio from 0.67 to 2.0, a gradual reduction of diamond grain size from micrometer to nanometers scale was observed. The formation of nanocrystalline diamond (NCD) matrix can be attributed to the restricted diffusion of radical species and the diamond nucleation kinetics on copper substrates. By through-holes of templates on copper substrates to restrict the diffusion and transport of radical species, NCD matrix was successfully deposited on copper substrates.