Electrodeposition of Ni-Co composites containing nano-CeO_2 and their structure, properties

摘要

One of the most powerful rare earth oxides, ceria CeO_2 was incorporated in Ni matrix and the effect of cobalt addition in the matrix, on the structure and properties has been studied. The amount of cobalt incorporated in the Ni matrix was in the range of 25-85 wt.%. The presence of cobalt resulted in a marginal variation in CeO_2 content from 5 to 8 wt.%. The microhardness studies revealed that a maximum value of 540 Hk_(50gf) was obtained in the presence of 25 wt.% cobalt in Ni-CeO_2 matrix compared to 50 and 85 wt.% addition. The presence of 25 wt.% cobalt in Ni-CeO_2 matrix also improved its wear resistance as seen from Tribology studies. The wear products were identified using Raman Spectroscopy. The X-ray diffraction (XRD) studies showed that an increase in cobalt content from 25 to 85 wt.% resulted in a change in crystal structure from fcc to hcp. A change in surface morphology with variation in cobalt content was seen from scanning electron microscopy (SEM). It was perceived from the thermal stability studies that the presence of 85 wt.% cobalt in Ni-CeO_2 matrix imparted better stability in microhardness at temperatures up to 800℃. Although, the incorporation of cobalt in Ni-CeO_2 matrix enhanced the microhardness, wear resistance and thermal stability it did not improve the corrosion resistance as noticed from immersion corrosion studies.