## 1 Introduction  
Metal Injection Moulding (MIM) is a very well-known mass production technique for the processing of small to medium-sized metal parts with intricate shapes. It offers several advantages over other manufacturing processes, such as flexibility in design with minimal finishing operations, as well as reduced material waste [1]. These advantages have made MIM one of the most investigated processes for producing titanium parts, especially for biomedical applications. However, there are many obstacles towards the use of such technique in preparing Ti parts, such as the high cost of the fine powders used in the preparation of feedstock [2]. Another obstacle is the high reactivity of titanium at a relatively high temperature, where it reacts with the decomposed product of the binder during thermal debinding and sintering, resulting in high interstitial content [3]. Generally, powders with a particle size below 45 \(\upmu\)m are used in injection moulding in order to result in minimal porosity within the samples and a density near the theoretical density for improved mechanical properties [4]. However, the smaller the particle size, the higher the surface area and the more the Ti part is prone to contamination and oxygen pick up during processing, debinding and sintering. In addition, the use of fine powders can result in more shrinkage, as the smaller the particles used, the greater the rate of sintering or the rate at which bonding between the particles, neck formation and growth (as well as densification) occur [5]. One way to reduce this shrinkage and the extent of contamination, as well as lower the cost, is to use Ti powder with a relatively coarse particle size (>45 \(\upmu\)m). This will not only be more economical, but can also result in more intentionally-induced micropores. These micropores are advantageous, particularly for biomedical applications, where they promote bone ingrowth and cell attachment [6; 7]. Aside from promoting bone-implant integration, the presence of these pores can also play a significant role in reducing the stiffness of the Ti parts to match that of the bone in order to avoid the stress shielding phenomenon [8; 9]. Nevertheless, wear of the tools could be an issue in using coarse powders. [PERSON] and [PERSON] [10] studied the possibility of using coarse powders for MIM with particles as large as 62 \(\upmu\)m and concluded that it is possible to process them with reduced wear provided that an increased clearance was left between the bushing and the barrel. However, they did not report any details about the powders' rheological and shrinkage behaviour after sintering.  
The main aim of this study is to explore the use of a relatively coarse Ti powder to produce Ti parts by MIM with the potential for biomedical applications and compare it in terms of performance to a commercial Ti feedstock PolyMIM Grade 2. In addition, the rheological behaviour of both feedstocks and their volume shrinkage will be examined. Furthermore, the possibility of coating these Ti parts with amorphous ceramic coating using the plasma oxidation process will be explored in order to improve the bioactivity of the samples and result in accelerated cell-surface interlocking, as the Ti itself is bio-inert [11].