Papers by Author: Gang Zhang

Abstract: NiCrAlY coatings were deposited on CrNi3MoVA steel substrates by means of magnetron sputtering. The coatings were characterized in terms of their microstructure, hardness, friction coefficient, high-temperature oxidation resistance. Micro-indentation and tribometer testers were employed to measure the mechanical properties of NiCrAlY coatings and CrNi3MoVA steel. The results showed that the hardness of the coatings ranged from 5.7 to 5.9 GPa, with a higher value than that of CrNi3MoVA steel(4.1-4.3 GPa). The coefficient of steady-state friction of the coatings against 45-carbon-steel balls ranged from 0.35 to 0.40, with a lower value than that of CrNi3MoVA steel(0.63-0.68). The isothermal oxidation behavior at 850°C of the coatings were studied in comparison with CrNi3MoVA steel substrates. The results indicated that NiCrAlY coatings substantially increase the high-temperature oxidation resistance of CrNi3MoVA steel and the oxidation process was retarded mainly by the presence of outer complex oxide scales and a continuous Al₂O₃ inner layer on the coating.

Abstract: A novel and practical route for preparing carbon coating metal nanomaterials using polyvinyl alcohol as the starting materials was presented. Carbon coating iron nanoparticles can be effectively synthesized by carbonizing polyvinyl alcohol using Fe as catalyst in hydrogen flow. The carbohydrate was carbonized in a controllable way that leads to a large amount of carbon coating iron nanoparticles. Transmission electron microscopy (HRTEM), energy dispersive X-ray (EDX) and thermogravimetric analysis (TG) were employed to characterizing nanomaterials. The growth mechanism of carbon coating iron nanoparticles is briefly discussed in term of composition and structure of precursor.