Stable colloidal suspension of magnetic nanoparticles is challenging owing to both van der Waals forces and magnetic dipolar interactions.Thus, it is essential to coat magnetic nanoparticles with a surfactant during chemical synthesis in order to prepare well-dispersed nanoparticle colloid. In the present study, cobalt nanoparticles (∼15 nm in size) were synthesized with the fatty acid (oleic acid) as a surfactant. The chemical interaction of the surfactant with the Co nanoparticles was studied by using Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The results indicated that oleic acid gets chemisorbed as a carboxylate on the Co nanoparticle surfaces, and the two oxygen atoms in the carboxylate are coordinated symmetrically to the Co atoms, leading to the formation of the covalent Co−O bond. This result has implications for the strong interaction between the surfactant and Co nanoparticle, which enhances the stability of Co colloid.
Porous Ti6Al4V was attempted to be produced by using the protein forming method. This study
characterizes slurry compositions and processing parameters aimed to obtain porous Ti6Al4V with
open porosity, an interconnected porous networks and controllable pore size. Laboratory egg white
powder was used as a binding and a foaming agent. A porous Ti6Al4V green body was produced
through a gelling process at 80°C and a drying process at 120°C. A good strength porous Ti6Al4V
specimen is available after a protein burnout process in an air atmosphere and a sintering process in
a vacuum environment. Optical microscopy was performed on the porous Ti6Al4V specimens after
each processing step to inspect their porous structure. Carbon and oxygen contents were also
analyzed in the specimens during intermediate processing steps. Optimal temperature for protein
burnout process is identified to be between 400°C to 450°C for an egg white concentration in the
range of 6vol% - 24vol%. Pore sizes approximately 200–700 μm were observed after the sintering
process. These experimental results demonstrate prospects on fabricating porous titanium and other
metals using the protein forming method.
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