We report on the synthesis and characterization of ZrO 2 nanoparticles prepared from zirconium(IV) butoxide in the absence of base or acid mineraliser by an advanced oxidation processes (AOP) and subsequent hydrothermal treatment which involves mixing and dissolution of the precursor for different temperatures. The structure, morphology and properties of the nanoparticles were characterized using XRD, FE-SEM, TEM, HRTEM, Raman spectroscopy, FT-IR spectroscopy, BET measurements and TGA measurements. The structural analysis by XRD and Raman spectroscopy confirms the ZrO 2 specimens synthesized at 100 C for 1 hour are amorphous and those treated at 150 C and 200 C for 1 hour were crystalline. Structural analysis by Raman spectroscopy confirms tetragonal ZrO 2 specimens obtained at temperatures higher than 100 C as a majority phase. From FE-SEM images, the AOP/hydrothermal route mainly produced microspheres comprised of primary nanoparticles. HRTEM images of ZrO 2 microspheres, after treatment at 100 C, show the beginning of crystallization, with only a few clear lattice fringes dispersed in the specimens. TEM and HRTEM images of ZrO 2 , after treatment at 150 C and 200 C indicate that the microspheres are the aggregation of small nanoparticles with a size of approximately 5-8 nm, and FFT analysis confirms the high crystallinity of the specimens. TGA analyses show a distinctive behavior for each of the ZrO 2 specimens, after treatment at 100 C, 150 C and 200 C. FT-IR analysis of ZrO 2 specimens after hydrothermal treatment revealed the presence of groups, such as -OH, -CH 2 , and -CH at the surface. In addition, FT-IR spectra show a decrease in the amount of functional groups attached to the surface of the nanoparticles when the reaction temperature is increased. This result was also confirmed by TGA analysis. The ZrO 2 specimens prepared by the AOP/ hydrothermal route exhibited a high surface area of 511-184 m 2 g À1 .

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This study investigates the influence of particle size on the solid-solid transition in zirconium (ZrO 2) nanoparticles. The Simultaneous Thermogravimetry/Derivate Thermogravimetric-Differential Thermal Analysis (TG/DTG-DTA) was used to evince the phase transitions processes as well as the quantity of volatile compounds and the residual organic matter formed during the synthesis of nanoparticles. Field Emission Scanning Electron Microscopy (FE-SEM) and Transmission Electron Microscopy (TEM) were used to prove the increase and agglomeration ;1;of particle size after each thermal cycle.

This study aimed to produce and characterize the microstructure and mechanical properties of dense polycrystalline bovine hydroxyapatite (DPBHA) bioceramics with 5% and 8% of TiO 2 nanoparticles after final synthetization for future use in dental implants. Structural characterization was obtained from analyzes by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscope, energy dispersive spectroscopy, and relative density and apparent porosity. The mechanical characterization was performed by measuring the fracture toughness after three-point flexural strength (FS) test. The microstructural characterization results showed no secondary phase formation and nonhomogeneous nanoparticle dispersion in HA matrix. DPBHA/Np8% (2.9 ± 0.09 g/cm 3 ) exhibited significantly greater density than DPBHA (2.7 ± 0.03 g/cm 3 ) (p = 0.011) and DPBHA/Np5% (2.7 ± 0.05 g/cm 3 ) (p = 0.041). DPBHA (0.9%) had the smallest porosity followed by DPBHA/Np8% (3.4%). DPBHA/Np5% (4.5%) exhibited the greatest proportion of pores. Pure HA (51.7 ± 10.3 MPa) and DPBHA/Np8% (47.4 ± 6.4 MPa) had significant greater FS (p < 0.001) than DPBHA/Np5% (28.8 ± 3.1 MPa). DPBHA (0.43 ± 0.01 MPa m 1/2 ) and DPBHA/Np8% (0.40 ± 0.06 MPa m 1/2 ) presented greater KIc than DPBHA/Np5% (0.23 ± 0.02 MPa m 1/2 ) (p < 0.003; p < 0.007). In conclusion, 8% TiO 2 nanoparticle addition to this synthesis would be a promising HA blend, as mechanical properties were similar, and the relative density/apparent porosity showed superior results than those of the DPBHA.

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