Ultra-fine hydroxyapatite (HA) powders were produced with radio frequency (RF) suspension plasma spraying (SPS). This novel technique utilizes the inherent properties of the RF plasma enabling axial feeding of the suspension into the plasma producing spherical ultra-fine HA powders. These powders were examined by XRD and Rietveld analysis using the Rietquan 2.3 Quantitative Analysis software package. The aim of the analysis was to determine the various amounts of decomposed phases and amorphous content after SPS of HA. Results showed that the amount of decomposed phases rose up to a plate power of 15 kW there after decreasing at higher plate powers. The amorphous phase however kept increasing with plate power reaching about 35 wt.% in the powders sprayed at 21 kW. These trends have led to the belief that the phase content and hence, the characteristics of the powders are controlled mainly by the competitive processes of decomposition and melting and evaporation within the plasma. The morphology of the powders was also observed through TEM and changes in molecular structure were investigated by FTIR. DSC was carried out to observe the crystallisation of amorphous calcium phosphate into HA.

Polyphenylene-sulphide (PPS) and polyphenyletheretherketone (PEEK) have high heat and corrosion-resistant performance. Thermal sprayed coatings of PPS and PEEK have been produced by the HVAF spray system. The molecular structures of these coatings have been analyzed by Fourier Transform Infrared Spectrophotometer (FT-IR) and Differential Scanning Calorimeter (DSC). The microstructures of cross-section and surfaces of these coatings have been observed. The formation mechanism of these coatings has been estimated as follows; (1) PPS and PEEK powders are melted and oxidized during thermal spraying. However, the amount of coating oxidation is very small, so that high anti-corrosion performance of sprayed coatings is obtained. (2) These coatings have some pores including the incomplete melting particles. However, it is estimated that these pores are closed-pores.