Fabrication And Characterization Of Cobalt-Diamond-like-Carbon (Co-DLC) Nanocomposites

In recent years, synthesis of magnetic nanocomposites has been receiving significant attention. These nanocomposites offer opportunities to develop active nanomaterials with various applications like magnetic data storage and biomedical applications. They can be designed to provide excellent magnetic properties. However, high saturation magnetization materials, such as Co are not biocompatible. Thus, designing nanocomposites with magnetic phase embedded in biocompatible protective shells is of immense interest. In this study, Co-DLC nanocomposites were synthesized using a hybrid CVD/PVD technique and different combination of processing parameters were used to vary the concentration of Co in the nanocomposites. X-ray photoelectron spectroscopy showed, that with increase in the Co content from 50 at% to 65 at% the sp3/sp2 ratio decreases from 1.3 to 0.87 that consequently decrease hardness from 11.3 GPa to 9 GPa. An increase in the Co content was observed to increase the coefficient of friction. TEM images for all the nanocomposites from 25 at% to 65 at% showed Co nanocolumns encapsulated by DLC matrix. The nanocolumn exhibited wide variation from 6 nm to 14 nm. As-deposited Co-DLC was found to have ε-Co and DLC matrix. Magnetic measurements for as-deposited films illustrated that, nanocomposites with lower Co content and having small particles size shows superparamagnetic behavior, whereas nanocomposite with higher Co content of 65 at% showed ferromagnetic behavior. On annealing at 250oC and 500oC, all the nanocomposites exhibited ferromagnetic behavior accompanied by increase in the coercivity and saturation magnetization. On annealing at 500oC, nanocomposite with 65 at% Co showed dramatic increase in the saturation magnetization and coercivity. Thus, annealing treatment can be used to tailor the magnetic properties of the nanocomposites and makes it suitable for various applications like sensor and biological.