In this study, a hydroxyapatite (HA) coating derived from the scales of the Amazonian fish pirarucu (Arapaima gigas) was produced using calcination at 500 and 750 °C and deposited on AISI 316 stainless steel substrate using the process of thermal spraying, high velocity suspension plasma spray (HVSPS). To verify its potential, this material was characterized by X-ray diffraction (XRD), by which characteristic peaks of hydroxyapatite were evidenced. Via X-ray fluorescence (XRF) of the samples, it was observed that the Ca/P ratio was equal to 2.00. Using the Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopy, it was possible to observe the characteristic bands of the HA. For the coating, the mechanical nanoindentation test showed mean Vickers microhardness (VH) values of 93.25 VH for the hydroxyapatite and of 196.57 HV for the substrate. The modulus of elasticity (EIT) was 77.85 GPa for the hydroxyapatite coating and 136.45 GPa for the substrate. Optical microscopy showed that the coating was homogeneously deposited.

Abstract Solid residues from agroindustry often accumulate and cause environmental imbalance. An alternative to this is to use this residue as a reinforcement in polymers. The achievement of this work was to characterize a composite with a polystyrene matrix reinforced with Brazil nut shells residues. The residues were cleaned and ground to then produce the samples via injection molding with the proportions of 0%, 2.5% and 5% of load. The specimens were characterized using mechanical tensile testing and thermogravimetric analysis (TGA). The mechanical test showed that the composite with 2.5% of filler had greater stiffness and strength was improved by 5%. Thermal analysis showed an increase in the temperature for the beginning of the degradation of the M2.5 composite. The results confirm a potential application in the automotive industry for the polystyrene composite reinforced with Brazil nut shells.

Abstract This study evaluated the influence of cellulose nanocrystals (CNC) content on the properties of epoxy nanocomposites. The CNC were obtained from microcrystalline cellulose by acid hydrolysis. 4.0, 5.5 and 7.0% of untreated CNC were incorporated into epoxy resin. Sonication was used to disperse the CNC in the resin. The thermal stability, the glass transition temperature and the degree of conversion were reduced as observed by Thermogravimetry and Differential Scanning Calorimetry, respectively. The tensile and bending modulus showed no significant improvement and the impact resistance showed a slight reduction due to the non-uniform dispersion of the CNCs, as observed by Transmission Electron Microscopy. Analysis of Scanning Electron Microscopy showed a change of the fracture mechanism of the epoxy resin: the CNCs increased the elastic modulus by reinforcement, but accelerated the fracture by acting as defects. The Halpin-Tsai model was applied to predict the elastic modulus of the epoxy/CNC system.