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Taking the wide band gap one-dimensional (1-D) tungsten oxide nanowires as an example, we here demonstrate systematically the physical characteristics of thermally processed nanowires at temperatures ranging from 400°C to 1000°C, for the first time. Accompanied by a significant drop of specific surface area from 151 m²/g for the as-prepared nanowires to 109 m²/g and 66 m²/g subject to annealing at 400°C and 450°C, dramatically morphology evolution and phase transformation have also been observed. The nanostructured bundles became straighter, larger in diameters and shorter in length, and eventually became irregular particles with size up to 5 µm. The Brunauer-Emmett-Tettler (BET) result suggests that 400°C can be considered as a top temperature limit in nanodevice design where high surface area is important, e.g. in gas sensors. A protocol for thermally processing of these bundled tungsten nanowires has been established.

The mechanical inadequacies of calcium phosphates, such as hydroxyapatite (HA), for load bearing medical implant applications has been extensively documented. Conversely, poly(etheretherketone) (PEEK) is a semi-crystalline polymer with excellent mechanical properties, high chemical resistance and good thermal stability. Hence, composite formulations combining the properties of PEEK with the bioactivity of HA, may have potential for use in load bearing implants. However, since the utilisation of such systems requires processing at relatively high temperatures (≈ 400°C), it is important that any changes to the polymer that might be caused by the presence of the bioceramic component be fully understood.

In this study, the thermal stability of a series of precursor PEEK/HA composite mixtures has been investigated by conventional and modulated DSC methods. In addition, the materials of interest have been characterised by FTIR, XRD and high resolution XPS, as a function of temperature. Modulated DSC has provided an accurate means of determining the effect of the bioceramic phase on PEEK crystallinity. This is due to the ability of the technique to provide an accurate measure of the polymer glass transition (T_g) and crystallisation (T_c) temperatures. From these data it has been possible to show that the presence of HA, even at compositions comprising ≈ 90 % wgt/wgt HA, does not adversely effect the % crystallinity of the PEEK over the DSC temperature range. These findings are supported by the chemical and structural analyses, which indicate no significant adverse effects on the PEEK from the presence of HA.