Cellulose fiber was isolated from bengkoang (Pachyrhizus erosus) tuber peel. A suspension consisting of distilled water, starch, and glycerol was mixed with various cellulose loadings (0, 2, 6, and 10 g) then gelatinized using a hot plate with a magnetic stirrer. The biocomposite gel was sonicated using an ultrasonication probe (47.78 W/cm² for 4 min). Scanning electron microscopy (SEM) micrographs for the fracture surface of resulting biocomposite films displayed a rougher surface than starch film, indicating fiber dispersion in the matrix. The opacity and moisture resistance of biocomposite films increased with the addition of cellulose. The opacity was at a maximum value (243.05 AUnm) with 10 g fiber, which was 11.27% higher than the starch film without cellulose. Moisture absorption of this biocomposite was 16.79% lower than the starch film. Fourier transform infrared (FTIR) confirmed this more hydrophobic nature with lower transmittance at –OH stretching in the composite than the starch film. The addition of cellulose fiber into the matrix also increased the crystallinity index.

One of factor causing the failure of Ti-6Al-4V Extra Low Interstitial (ELI)-based material implants, does not have bioactive properties in the implantation process, thus not supporting the osseointegration process in the body. For this reason, coating with hydroxyapatite (HA) suspension is necessary. This research used the dip-coating method and added Zirconium Oxide (ZrO₂) into nanosized commercial HA to be suspensions (17%wt and 20%wt) to strengthen the adhesion of the coating. The specimens were heated at 800, 900, and 950°C to densify the layers. Bioactivity increased along with the increasing calcium/phosphate (Ca/P) ratio of the HA layers in the test specimens. The specimens were immersed in Simulated Body Fluid (SBF), namely Hank’s Solution, for 1, 2, 3, and 4 weeks. ZrO₂ added to the HA suspensions of Ti-6Al-4V ELI can increase the Ca/P ratio from 1.51 in the first immersion week to 1.62 in the fourth. The bioactivity level is also proven by the accumulation of calcium and phosphate on the surface of the coating. The Ca/P value close to the Ca/P ratio of HA of 1.67 is good for improving the osseointegration process in the body.

Corrosion on wooden nails is very detrimental because it shortens the life of the ship. Although the used spikes have been coated with corrosion resistance material, corrosion rate is still very harmful. Therefore that additional effort is required for reducing the corrosion rate of these spikes. Research has been done by comparing the giving of cocoa peels extract as a paint mixer to corrosion rate. As a comparison has also been done nails without paint and nails painted without additional cocoa peels extract. Calculation of corrosion rate is done by weight loss method. The addition of cocoa peels extract showed significant effect on corrosion rate, it can be explained cocoa peels containing secondary metabolite compound one of them is tannin. The tannin compound in the extract can form complex compounds with Fe (III) on the metal surface, so that the corrosion reaction rate will decreas.Keywords: cocoa peels extract, corrosion, weight loss.

Ti-6Al-4V Extra Low Interstitials (ELI) is one of the most widely used titanium alloys for orthodontic and orthopedic implants. However, several studies reveale