ABSTRACT
A new approach of using a polymer hybrid nanocomposite coating to modify the surface of titanium and its alloys is explored in this study. Electrostatic spray coating process is used to deposit the coating on the plasma-treated substrates for better adhesion. Ultra-high molecular weight polyethylene (UHMWPE) has been selected as the parent matrix for the coating due to its biocompatibility and excellent tribological properties. However, to improve its load-bearing capacity carbon nanotubes (CNT's) (0.5, 1.5, and 3 wt.%) are used as reinforcement and to further enhance its performance, different weight percent of hydroxyapatite (HA) (0.5, 1.5, 3, and 5 wt.%) are introduced to form a hybrid nanocomposite coating. The dispersion of CNT's and HA was evaluated by Raman spectroscopy and scanning electron microscopy. The electrochemical corrosion behavior of the nanocomposite coatings was evaluated by performing potentiodynamic polarization and electrochemical impedance spectroscopic tests in simulated body fluid. Tribological performance of the developed hybrid nanocomposite coating was evaluated using a 6.3 mm diameter stainless steel (440C) ball as the counterface in a ball-on-disk configuration. Tests were carried out at different normal loads (7 N, 9 N, 12 N, and 15 N) and a constant sliding velocity of 0.1 m/s. The developed hybrid nanocomposite coating showed excellent mechanical properties in terms of high hardness, improved scratch resistance, and excellent wear and corrosion resistance compared to the pristine UHMWPE coatings.
ABSTRACT
Hydrophobizing of stretchable elastomer surfaces is considered and the reversible behavior of the resulting surface wetting state is examined after stretching and relaxing the hydrophobized samples. The environmental dust are analyzed in terms of elemental constitutes and size, and the dust pinning on the hydrophobized surface is measured. The dust removal mechanisms, by the water droplets on the hydrophobized surface, are investigated. We demonstrated that deposition of functionalized nano-size silica units on the elastomer surface gives rise to hydrophobicity with 135° ± 3° contact angle and low hysteresis of 3° ± 1°. Stretching hydrophobized elastomer surface by 50% (length) reduces the contact angle to 122° ± 3° and enhances the hysteresis to 6° ± 1°. However, relaxing the stretched sample causes exchanging surface wetting state reversibly. Water droplet rolling and sliding can clean the dusty hydrophobized surface almost 95% (mass ratio of the dust particles removed). Droplet puddling causes striations like structures along the droplet path and close examination of the few residues of the dust reveals that the droplet takes away considerably large amount of dust from surface.
