N-doped carbon material modified with cobalt nanoparticles as catalyst for oxygen reduction

In the present study, carbon-derived material from pulping residues, such as black liquor, was doped with a cheap nitrogen precursor, dicyandiamide, and after that modified with cobalt nanoparticles using electroless metal plating. The morphology, structure and composition of the synthesised catalyst was characterised using TEM, XPS, Raman Spectroscopy and ICP-OES, whereas the activity of the prepared catalyst was evaluated for the electro-reduction of oxygen in an alkaline medium by employing the rotating disk electrode method. It has been determined that modifying of N-doped carbon material with cobalt nanoparticles results in enhanced activity for the oxygen electro-reduction as compared with that of pure N-doped carbon material.

Processing and Properties of ZrB2-Cu Composites Sintered by Hot-Pressing Sintering

ZrB2-Cu composite is a new electrical contact materials in the integration of high conductivity, high wear resistance and good mechanical strength. In this paper, ZrB2-Cu composites were prepared by hot-pressing sintering at 800~900 °C under a pressure of 20 MPa.The densification of ZrB2-Cu composites was improved by the addition of nickel using an electroless metal plating technique. X-ray diffraction and scan electron microscopy were used to analyze the phase and microstructure of ZrB2-Cu composites. The results showed that ZrB2-Cu composites with 60 vol % Cu which was sintered at 900 °C had a higher relative density, highest flexural strength of 381 MPa and higher hardness of 2.16 GPa(HV). ZrB2-Cu composites with 50 vol % Cu which was sintered at 900 °C had higher flexural strength of 297 MPa and the highest hardness of 2.66 GPa.