No abstract

The releases of harmful ions from cobalt based alloy to host tissues have raised significant health concerns. Carbon contents in this alloy may influence ions release but has yet investigated. It is hypothesized that carbon contents in this alloy will help the formation of oxide layer during thermal oxidation process and hence reducing the release of Co/Cr ions after implantation. In this study, Co-Cr-Mo alloy with carbon concentrations of 0.03% and 0.24% were oxidized at 1050°C for 3 hours under atmospheric condition. The oxidized substrates were characterized under FESEM and subjected to circulating immersion test in simulated body fluid (SBF) for 21 days. Metal ions release was measured using inductively coupled plasma-mass spectrometry (ICP-MS) at day 0, 7, 14 and 21. Oxidized high carbon samples show denser and a more uniform oxide layer than samples with low carbon contents. It is found that compact oxide structure promotes less metal ions release during immersion.

Areca leaf sheath has been used traditionally to produce disposable plates and bowls in India for decades. This project aims to produce disposable takeaway food containers by using the fallen Areca leaf sheath. In order to achieve the aim, a press mold is self-designed and fabricated, and installed into a disposable paper plate press machine to form the sheath into container shape. The density of the sheath is 0.423 g.cm−3 and 0.391 g.cm−3 before and after press respectively. The moisture content percentage obtained before heat press is 19.19%, while after press is 5.01%. The sheath at its sheath line direction shows higher stiffness, which is 416.9g.cm, compared to the perpendicular sheath direction of 65.1g.cm. The sheath has a water absorption rate of 0.021g.min−1, which fulfils the purpose of disposable food packaging to contain foods with soup or sauce.

This study analyses residual stress measurement using X-Ray diffraction method on ultrafine-polycrystalline diamonds and polycrystalline diamonds films grown using Hot Filament Chemical Vapour Deposition technique (HFCVD) on silicon nitride(Si3N4) and tungsten carbide (WC) substrates in the same chamber at the same time with varied pretreatments prior to HFCVD diamond deposition. Measurements were taken perpendicular to the surface and the measured residual stress states of the diamond films are in compression. Thus, assuming isotropic properties of the film, the diamond films grown have tension residual stress parallel to the surface of the substrate. Residual stress is estimated to have the lowest stress for substrate that has undergone 5g/liter silicon carbide seeding process. Effects of residual stress to adhesion are discussed for both substrates.

Multi-layer alternating nanocrystalline diamond (NCD) layer and polycrystalline diamond (PCD) layer was successfully deposited on pretreated tungsten carbide (WC) substrates with various seeding sizes (<0.1μm synthetic, <0.5μm synthetic, <0.25μm natural, <0.5μm natural, and <1μm natural) diamond with and without hammering by silicon carbide. X-rays penetrate through the coating to the substrate from XRD method was able to show strong peaks of diamond relative to WC despite the diamond film being 4μm thick only. It is found that substrates with no hammering produce stronger signals. The coating was cross sectioned and analysed using field emission scanning electron microscopy showing the multi-layer with NCD grains that has coalesced and columnar structure for PCD. None of the diamond coating delaminated during cross sectioning showing good adhesion. Raman was able to capture data from the 1-1.6μm thick NCD layer only while AFM measured the extreme low roughness of the NCD surface.