Purpose: This study aimed to decorate the surface of TiO₂ nanotubes (TiO₂ NTs) grown on medical grade Ti-6Al-4V alloy with an antimicrobial layer of nano zinc oxide particles (nZnO) and then determine if the antimicrobial properties were maintained with a final layer of nano-hydroxyapatite (HA) on the composite. Methods: The additions of nZnO were attempted at three different annealing temperatures: 350, 450 and 550 °C. Of these temperatures, 350°C provided the most uniform and nanoporous coating and was selected for antimicrobial testing. Results: The LIVE/DEAD assay showed that ZnCl₂ and nZnO alone were >90% biocidal to the attached bacteria, and nZnO as a coating on the nanotubes resulted in around 70% biocidal activity. The lactate production assay agreed with the LIVE/DEAD assay. The concentrations of lactate produced by the attached bacteria on the surface of nZnO-coated TiO₂ NTs and ZnO/HA-coated TiO₂ NTs were 0.13±0.03 mM and 0.37±0.1 mM, respectively, which was significantly lower than that produced by the bacteria on TiO₂ NTs alone, 1.09±0.30 mM (Kruskal–Wallis, P<0.05, n=6). These biochemical measurements were correlated with electron micrographs of cell morphology and cell coverage on the coatings. Conclusion: nZnO on TiO₂ NTs was a stable and antimicrobial coating, and most of the biocidal properties remained in the presence of nano-HA on the coating.

Composite coatings are commonly applied to medical metal implants in order to improve biocompatibility and/or bioactivity. In this context, two types of titanium-based composite coatings have been reviewed as biocompatible and anti-bacterial coatings. The different composites can be synthesised on the surface of titanium using various methods, which have their own advantages and disadvantages. Moving with the smart and nanotechnology, multifunctional nanocomposite coatings have been introduced on implants and scaffolds for tissue engineering with the aim of providing more than one properties when required. In this context, titanium dioxide (TiO₂) nanotubes have been shown to enhance the properties of titanium-based implants as part of nanocomposite coatings.

Polyamide 11 (PA11) is a plant-based nylon made from castor beans. Powder bed fusion laser sintering (PBF-LS) is an additive manufacturing process used for PA11 which allows for the reuse of the unsintered powder. The unsintered powder is mixed with virgin powders at different refresh rates, a process which has been studied extensively for most semi-crystalline polyamides. However, there is lack of information on the effect of using 100% reused PA11 powder and the effect of the number of times it is reused on its own, during powder bed fusion laser sintering. This paper investigates the effect of reusing PA11 powder in PBF-LS and the effect of the number of times it is reused on the dimensional accuracy, density and thermal and tensile properties. From the 100% virgin powder to the third reuse of the powder, there is a decrease in powder wastage, crystallinity and tensile strength. These are associated with the polymerisation and cross-linking process of polymer chains, upon exposure to high temperatures. This results in a higher molecular weight and, hence, a higher density. From the fourth reuse to the tenth reuse, the opposite is observed, which is associated with an increase in high-viscosity unmolten particles, resulting in defects in the PBF-LS parts.

This paper discusses the microstructure effects on the machinability of Inconel 718 by conducting machining tests on an additively manufactured (AM) workpiece with a strongly textured grain structure and a wrought workpiece incorporating a finer and more equiaxed grain structure. The AM workpiece was produced as a thin tube using Laser Melting Powder Bed Fusion and optimal processing conditions for this alloy. A lathe was used to conduct instrumented orthogonal machining tests on the two workpiece materials under dry cut and coolant conditions using a semisynthetic emulsion coolant. The process parameters studied were feed from 0.05 to 0.15 mm/rev and cutting speed from 60 to 120 m/min with a cut time of 2 sec duration for each process condition. Measures for each process condition included cutting forces in the feed and main cut direction, and images of chip forms were obtained. The grain structures of the workpiece materials were characterized using Electron Back Scattered Diffraction (EBSD). New findings suggest that grain structures can significantly affect the machinability of the superalloy at a higher feed for all cutting speeds studied, and insights into the cause are discussed. Other important findings comment on the effectiveness of the coolant as a lubricant for reducing friction in machining.