Microporous Titanium through Metal Injection Moulding of Coarse Powder and Surface Modification by Plasma Oxidation

Titanium is one of the most attractive materials for biomedical applications due to having excellent biocompatibility accompanied by good corrosion resistance. One popular processing technique for Ti is Metal Injection Moulding (MIM). However, there are several issues associated with the use of this technique, such as the high cost of the fine powder used, the high level of contamination and consequent alteration to material properties, as well as the large volume shrinkage that occurs during sintering. In this study, the use of a relatively coarse Ti powder with a mean particle size of 75 μm to process Ti parts with the potential for biomedical applications by MIM will be examined, compared to a commercial Ti feedstock, and subsequently coated using Plasma Electrolytic Oxidation (PEO). The results show that samples produced with the coarse powder shrink 35% less and have a relative density 14% less with an average pore size three-times larger than that of the commercial feedstock. This helps increase the potential competitiveness of MIM in the production of biomedical parts, as it reduces cost, shrinkage and results in more intentionally-induced micropores, such as are desired for biomedical implants. PEO treatment of the samples yields a thick rough coating comprised of a mixture of rutile and anatase with interconnected microporous channels and openings resembling the mouth of a volcanic crater

Production and digital image correlation analysis of titanium foams with different pore morphologies as a bone-substitute material

Ti foams are mesoporous structured materials that are characterized by their high surface area and interconnected porosity with a huge potential for biomedical applications. In this study, we investigated the production of titanium foams with different pore morphologies as a bone-substitute material via the addition of different amounts, shapes, and sizes of the space holder. Furthermore, we also carried out strain analysis using digital image correlation (DIC) in order to analyse the strain distribution across the porous samples. In addition, the nature of the relationship between the amount of the space holder added and final amount of porosity in the foams produced was also examined. The results demonstrated that the relationship between the space holder amount and porosity in the samples follows a complex one-phase exponential decay function in an increasing form. Our findings also suggest that the shape of the space holder does not play a significant role in dictating the porosity of the foams produced in the current study. However, the space holder’s shape does have a substantial role in dictating the mechanical properties of the foams produced, where Ti foams produced using a cubic or irregular space holder were found to have a lower yield stresses than those made with the spherical space holder

Structural characterisation of porous copper sheets fabricated by lost carbonate sintering applied to tape casting

In this article, we describe experimental investigations of the structural characterisations of double-layered porous copper tapes of thickness down to 0.74 mm. The porous sheets were produced by a process combing tape casting and lost carbonate sintering (LCS) to control both the porosity and pores distribution of the sheets. By varying the values of processing parameters, double-layer (porous and dense) structured tapes with open cell structure and porosities ranging from 50.0 to 81.5% are produced. Scanning electron microscopy and actual size image analysis were employed to measure the pore size and surface porosity of the porous sample. The pore size distribution was characterised using Micro-CT scanner running Skyscan NRecon software and CTAn software. A helium pycnometer was employed to obtain the bulk porosity of the porous copper samples. Statistical analysis of these measurements was used to assess the efficiency and consistency of the space holder technique used to generate porosity, as well as to draw information about the influence that different processing routes have on the resulting mesostructure of the porous copper metal, and on its properties