Amount Of TCP Research Articles

Impact of Gamma Irradiation on the Properties of Magnesium-Doped Hydroxyapatite in Chitosan Matrix.

This is the first report regarding the effect of gamma irradiation on chitosan-coated magnesium-doped hydroxyapatite (xMg = 0.1; 10 MgHApCh) layers prepared by the spin-coating process. The stability of the resulting 10 MgHApCh gel suspension used to obtain the layers has been shown by ultrasound measurements. The presence of magnesium and the effect of the irradiation process on the studied samples were shown by X-ray photoelectron spectroscopy (XPS). The XPS results obtained for irradiated 10 MgHApCh layers suggested that the magnesium and calcium contained in the surface layer are from tricalcium phosphate (TCP; Ca3(PO4)2) and hydroxyapatite (HAp). The XPS analysis has also highlighted that the amount of TCP in the surface layer increased with the irradiation dose. The energy-dispersive X-ray spectroscopy (EDX) evaluation showed that the calcium decreases with the increase in the irradiation dose. In addition, a decrease in crystallinity and crystallite size was highlighted after irradiation. By atomic force microscopy (AFM) we have obtained images suggesting a good homogeneity of the surface of the non-irradiated and irradiated layers. The AFM results were also sustained by the scanning electron microscopy (SEM) images obtained for the studied samples. The effect of gamma-ray doses on the Fourier transform infrared spectroscopy (ATR-FTIR) spectra of 10 MgHApCh composite layers was also evaluated. The in vitro antifungal assays proved that 10 MgHApCh composite layers presented a strong antifungal effect, correlated with the irradiation dose and incubation time. The study of the stability of the 10 MgHApCh gel allowed us to achieve uniform and homogeneous layers that could be used in different biomedical applications.

The influence of Sr and Mn incorporated ions on the properties of microwave single- and two-step sintered biphasic HAP/TCP bioceramics

The aims of this study were to investigate the effects of Sr- and Mn-doped ions on the sintering behaviors, microstructure and mechanical properties of the bioceramics processed by single- and two-step microwave sintering (MWSSS and MWTSS). Nano-sized calcium hydroxyapatite powders doped with Sr and Mn ions, obtained by modified precipitation synthesis, were isostatically pressed at 400 MPa and processed by MWSSS and MWTSS at different temperatures. In all cases during the sintering, the doped HAP powders turned into biphasic mixtures of HAP and TCP, but the amount of TCP was certainly lower in the case of MWTSS. It was shown that the doped ions significantly affected: density, microstructure, grain size, porosity, hardness, and fracture toughness of the processed bioceramics. Two-step microwave sintering was successfully applied for the processing of HAP/TCP bioceramics doped with strontium and manganese ions. Both two-step microwave sintered doped bioceramics had similar and high hardness values, but the strontium-substituted bioceramic material certainly had higher fracture toughness (1.54 MPam1/2), with an average grain size of 195 nm. Based on the results presented in this paper, it was concluded that the two-step microwave sintered strontium-doped bioceramics could be suitable materials in the bone regenerative field.

Alloy Design of a New Type High-Performance P/M Turbine Disk Superalloy

The effects of alloy elements on the precipitation behaviours of TCP and γ’phases in new type powder metallurgy (P/M) turbine disk superalloy René104 at the aging temperature of 815°C were studied systematically by a thermodynamic calculation method. The chemical compositions of new type nickel-based P/M superalloy were designed combining with d-electron theory. The results show that the contents of Cr, Co, Mo and W mainly influence the precipitation temperature and amount of TCP and γ’phases in René104. The suggested contents of Cr and Co are 13% and 20.6% respectively, and the suggested content of Mo is higher than W. The results also show that the content ratios of Al/Ti and Nb/Ta affect the precipitation behaviours of TCP and γ’phases. The balance values of Al/Ti and Nb/Ta are suggested in order to make the alloy having desired microstructural stability and strengthening effect. In addition, Hf also influenced the precipitation behaviours of TCP and γ’phases and the suggested content of Hf is 0.2%. The main precipitates of the new type P/M turbine disk superalloy FGH98I are γ’, MC, M23C6 and M3B2, and no any TCP phases precipitate. After the exposure at 750°C, 815°C and 850°C for 1000h, the new alloy still shows good microstructural stability.

Effect of Ti on Microstructural Evolution of Re containing Single Crystal Superallys

The influence of titanium on the microstructural evolution of the rhenium containing second generation single crystal superalloys has been investigated by changing titanium content only. The results showed that with the increase of titanium, the percentage of γ/γ’ eutectic increased, initial melting temperature lowered, and the size of γ’ phase of the alloys after full heat treatment increased. Three-dimensional atom probe (3DAP) analyses showed that the addition of titanium increased the rhenium distribution ratio in γ and γ’ phase as well as the misfit of γ and γ’ phase, and hence to promote the γ’ phase rafting and growing up. The experimental results also showed that the amount of TCP (μ) phase precipitates increased gradually with the increase of the content of titanium during prolonged aging at 1093°C.

Microwave processing of functionally graded bioactive materials

A functionally graded material (FGM) that can function gradually with respect to bone tissue was fabricated by microwave processing by gradually changing the composition of calcium phosphates from the surface to the interior. Silver oxide (5 and 10 mol.%) was spread on the surface of compact hydroxyapatite (HA) powder and exposed to microwave irradiation. The sintered samples were found to contain tricalcium phosphate (β-TCP) and metallic silver (Ag) along with HA as evidenced by X-ray powder diffraction (XRD) study. The content of TCP and Ag gradually decreases with increasing depth from the surface. The FGMs formed by both microwave processing and by conventional heat treatment at 900 °C for 12 h with 5% Ag 2O were compared. The microwave processed FGM indicated more amounts of TCP and Ag on the surface and suggests the possibility of greater compositional control in FGM fabrication by microwave processing.