Muhammad Azizi Mat Yajid

Bio-corrosion behavior and mechanical characteristics of magnesium-titania-hydroxyapatite nanocomposites coated by magnesium-oxide flakes and silicon for use as resorbable bone fixation material

This study was aimed to improve of the corrosion resistance and mechanical properties of Mg/15TiO2/5HA nanocomposite by silicon and magnesium oxide coatings prepared using a powder metallurgy method. The phase evolution, chemical composition, microstructure and mechanical properties of uncoated and coated samples were characterized. Electrochemical and immersion tests used to investigate the in vitro corrosion behavior of the fabricated samples. The adhesion strength of ~36MPa for MgO and ~32MPa for Si/MgO coatings to substrate was measured by adhesion test. Fabrication a homogenous double layer coating with uniform thicknesses consisting micro-sized particles of Si as outer layer and flake-like particles of MgO as the inner layer on the surface of Mg/15TiO2/5HA nanocomposite caused the corrosion resistance and ductility increased whereas the ultimate compressive stress decreased. However, after immersion in SBF solution, Si/MgO-coated sample indicates the best mechanical properties compared to those of the uncoated and MgO-coated samples. The increase of cell viability percentage of the normal human osteoblast (NHOst) cells indicates the improvement in biocompatibility of Mg/15TiO2/5HA nanocomposite by Si/MgO coating.

Titania-carbon nanotubes nanocomposite coating on Mg alloy: microstructural characterisation and mechanical properties

ABSTRACT Atmospheric plasma spraying was carried out to deposit a bilayered NiCrAlY/nTiO2-CNT composite coating. Initially, NiCrAlY, as an under-layer with a thickness of around 100 µm, was deposited. Afterwards, nanostructured TiO2 (nTiO2), as an over-layer with a thickness of 135 μm, was deposited with and without the incorporation of carbon nanotubes (CNTs) on the Mg alloy surface. In contrast to NiCrAlY and NiCrAlY/nTiO2, the NiCrAlY/nTiO2-CNT nanocomposite coating displayed a higher bonding strength. The wear behaviour of the coatings was examined by the pin-on-disc test and the results revealed that the incorporation of CNTs into the nTiO2 coating considerably enhanced the tribological behaviour of Mg alloy due to the CNT’s bridging mechanism.

Maerogel: Alternative for Thermal Barrier Coating Topcoat

Thermal barrier coating (TBC) system has been developed for high temperature applications along with the used of yttria stabilized zirconia (YSZ) as topcoat. Recently, developing coating material made from nanoparticles is widely explored. Thus, maerogel could become a potential candidate for this purpose because it consists of nano porous particle with low in density and low in thermal conductivity. The coating is expected to improve the formation of thermally grown oxide (TGO), thermal stability and increase the insulating capability. However, maerogel need agglomeration process before coating can be made because of it has low mass and high specific area.

Investigation of Intermetallic Phase Formation and Structural Analysis in Annealed Al/Cu Bilayer Thin Films

The growth of intermetallic phases in Al/Cu bilayers thin film having 2/3 layer thickness ratios were characterized by X-ray powder diffraction (XRD), energy dispersive X-ray (EDX) and transmission electron microscopy (TEM). In annealing temperature of 200 °C, the growth is controlled by Cu diffusion which resulted to formation of θ-Al2Cu, η-AlCu, ζ-Al3Cu4 and γ-Al4Cu9 phase.