Obtenção, caracterização e deposição da hidroxiapatita obtida a partir da escama do pirarucu utilizando o processo high velocity suspension plasma spray (HVSPS)

Abstract

In this study, two samples were obtained by the thermal treatment of calcination of the pirarucu scale, calcined at 500°C and 750°C, aiming to obtain hydroxyapatite (HA), which is a bioceramic with bioactive characteristics of interaction with living organism. In order to verify the potential of this material obtained, as an alternative to synthetic (commercial) HA, using the high velocity suspension plasma sparay (HVSPS) thermal spray process for surface treatment of AISI 316L stainless steel. For the characterization of the samples were used the techniques of X - ray fluorescence, X - ray diffraction, Fourier transform infrared spectroscopy - FTIR and Raman spectroscopy. The results showed by fluorescence a Ca/P=2.0 ratio, characteristic of tetracalcium phosphate - TeCP, attributed to the presence of organic material affecting the relationship. The X-ray of the in natura scale proved the presence of HA in the amorphous phase with the influence of fiber and collagen organic matter. The calcined sample at 500°C showed the amorphous calcium phosphate phase - ACP with characteristic peaks of HA. In the calcined sample at 750°C it was possible to observe characteristic peaks of crystalline HA. There was also a characteristic peak of the tricalcium phosphate phase - TCP in the allotropic form β-TCP. The bands of vibrational modes v1, v2, v3 and v4 of groups (PO4-3) and (OH−) were evidenced in both FTIR results. Carbonate ion (CO3-2) characteristic bands were observed in the region between 1600 - 1300 cm-1, associated with impurity, characteristic of carbonated HA. Only the sample calcined at 750°C was characterized by Raman spectroscopy. V - bands of the P - O bonds with intense peak of symmetrical stretching were observed at 960 cm-1, and P - O of anti - symmetrical stretching in the bands 1026 cm-1, 1043 cm-1 and 1075 cm-1. O - P - O at 578 cm-1, 585 cm-1 and 605 cm-1 attributed to anti-symmetrical vibrations and O - P - O connections at 428 cm-1 and 447 cm-1 associated with deformation modes, which clearly indicate the presence of HA phase in the sample. In the 1075 cm-1 band, the presence of ions (CO3-2) can be observed, as well as in the FTIR. For application in the HVSPS process it was necessary to disperse the powder in distilled water. It was observed by XRD, after spraying, that there was maintenance of the crystallinity of HA, and the elimination of the tricalcium phosphate phase (TCP-β). The microindentation test showed average values of vikers microhardness (HV) and modulus of elasticity (Eit) of 93.25 HV and 77.85 GPa for HA coating, respectively. The fact that the sample obtained remains crystalline after thermal spraying, presenting the HA phase, under the surface of the substrate used, reveals the potential of this sample as an alternative to synthetic HA.