Estimation of plasma parameters in the process of micro-scale powder plastic and characteristic of its products

The temperature and density of plasma jets were estimated with a Boltzmann plot and Stark broadening of Ar I (696.54 nm) lines by optical emission spectroscopy (OES) in the process of plasma plastic, and the morphology and microstructure of tungsten (W) powders were investigated by scanning electron microscope (SEM) and x-ray Diffraction (XRD), respectively. The results show that the assumption of local thermodynamic equilibrium (LTE) was invalid at the end of the plasma jets, and earlier than this after the injection of tungsten powder. The temperature and electron density of the plasma jets were up to about T = 6797 K with Q(c) = 50 slpm and n(c) = 1.05 x 10(16) cm(-3) with Q(s) = 115 slpm at Z = 60 mm, respectively, and both dropped rapidly with the injected tungsten powders of 20 mu m. After the plasma plastic process, the spherical tungsten powders were prepared and there were some satellite particles on the surface of the spherical products. The tungsten powders were both composed of a single equilibrium alpha-W phase with a body centered cubic (bbc) crystal structure before and after plasma treatment.