Characterization and Effect of Anatase on Nano- Hydroxyapatite

The main bone substitute is hydroxyapatite either mineral or synthetic. Synthetic hydroxyapatite is produced by various methods such as, sol-gel, mechanochemical, hydrothermal, sonochemical, ceramic (wet and dry roads, routes through cements of calcium phosphates and route using emulsions-microemulsions), and hydrolysis. Hydroxyapatite obtained by wet via has features from micro to nano. It has been reported that adding titania mechanical properties of hydroxyapatite improve. In this study only the experimental evidence is presented. The objective of this study was to analyze the effect of anatase in synthetic hydroxyapatite obtained by co-precipitators. Powders were subjected to uniaxial and isostatic cold pressing to form pills. Later pills were sintered. The characterization of the material includes several techniques. It was compared with each of the different percentages of anatase 0.1, 1.5, 1, 3, 5, 7 and 10. The results show the existence of an optimum percentage by which the mechanical properties surpass others, maximum of hardness before immersed it in simulated body fluid with 7%. The explanation of this optimum is the presence of calcium titanate because of titania diffuses efficiently in the network hydroxyapatite. Characterization and Effect of Anatase on NanoHydroxyapatite


Introduction
Studies have shown that microcrystalline HA is known as a substitute "good-builder" with higher calcium absorption. It is a charge of second-generation calcium derived from bovine bone. And it is more effective than calcium carbonate in slow bone loss [1,2].
The composition of the mineral HA stoichiometric be expressed as Ca 10 (PO 4 ) 6 (OH) 2 with a Ca / P = 1.67 relationship, while the HA deficient in calcium (CDHA) is CA 9 (HPO 4 ) (PO 4 ) 5 (OH), with Ca / P = 1.50. The latter is the one that is considered the most similar to human bones [3].
Biocompatibility tests [4,5] natural HA (bovine base) and titanium dioxide show regeneration and capillarity after a few weeks.
Nanometric and stoichiometric hydroxyapatite was prepared by wet via [6]. Later, TiO 2 anatase was added. The analysis was made on powder with heat treatment at 680°C in Ar atmosphere (HA cc) and pills. The powders were subjected to UP and CIP to form pills [7]. The pills %HAcc+%TiO 2 were sintered at 850°C. HA cc and TiO 2 median size were 175.9 and 293.6 nm, respectively. Using other technique, Kumar et al. [8] reported hardness and elasticity of 15.1 and 0.405 GPa by nano-indentation for a load of 100 mN over a coating of subsequent layers of %HA%TiO 2 (25%HA75%TiO 2 , 50%HA50%TiO 2 , 75%HA25%TiO 2 and HA). These layers were sintered at 900°C during a few minutes with functionally graded successfully. Before, HA was calcined at 800°C for 2 h. HA and TiO 2 median size are 7.46 and 1.37 µm, respectively.
Fidancevska et al. [9] mixed HA and titanium powder to produce porous bionert-bioactive composite ceramic and reported an optimum value at 15wt. % of TiO 2 but at 20wt. % the Young modulus decreased, the median size HA was 5 µm. This was the first evidence of an optimum value at micrometer particles.

Materials and Methods
The characterization of the material includes SEM-HR, TEM, TEM-HR, FTIR, Raman, TGA / DSC, XRD, BET / BJH, XPS, nanoindentation and Z-sizer. Figures 1 and 2a show anatase and rutile phases of TiO 2 and amorphous and crystalline HA sc in air, therefore inert atmosphere (Ar) must be used and not exceed the heat treatment of 680°C and sintering of 850°C. Upon heating in air, phosphates and carbonates appear in HA sc at 980°C and 630°C, respectively, Figure 2b. Thus, to obtain calcium titanate instead of calcium carbonate should control the rate of calcination and the atmosphere.
Micrographs increased x75000, SEM 10KV and 93.3pA. PANalytical XPert PRO (45KV, 40mA) was used. XPS k-alpha: Al-Kα 1486.6 eV and 10-8 mbars. Raman at 633 cm -1 . UP No. 714987 RAM DIA 600. Dade diameter was 1cm of steel 316L. CIP was made with a Yuken Model 334 press applied 400MPa during one cycle of four steps: Step 1: 0-100MPa, step 2: 101-200MPa, step 3: 201-300MPa and step 4: 301-400MPa. Time of step is 30 seconds. After the pills were sintered at 850°C in Ar atmosphere since 500°C during 1hr, heat up slop 5°C /min and heat slope down 6°C /min. Fourteen zones were studied for each pill after immerged in SBF. The SBF was made following the method of Oyane et al. [10].  To verify pore size in a nanometer range in Figure 7 and Tables 1 and 2 appear Nitrogen-Adsorption-desorption (BET/BJH) tests. Those showed mesoporosity with a maximum area reduction of 8.93% and maximum pore radii of 1.88 nm for HA95.

Results and Discussion
And particles average size distribution, Figure 8 shows that for anatase is 294nm, HAcc is 175.9nm, HA95cc is 293.6nm and HA90cc is 206.4nm. The 2-modal distribution for HA95cc is evidence of the spread of titania in the HAcc. The tetragonal crystalline structure of HA95cc and HA90cc is observed in the Figure 9. The anatase structure is tetragonal and HAcc is hexagonal, Figure 10, is expected that %HAcc+%TiO 2 are tetragonal. The morphology change is followed in Figure 11. The anatase into "balls" surrounding the cylindrical bars HAcc. This balance is in HA95cc and HA93cc.
Raman spectra show titanate ion together υ 3 anatase, and characteristic picks HAcc, Figure 12         Va/cm3 g-1 HA99cc Va/cm3 g-1 HA95cc Va/cm3 g-1 HA90cc       Tables 3 and 4, maximum hardness and elasticity are at HA93cc before SBF. They are minimums after 1 day into SBF. The maximum work of elasticity and plasticity are HA93cc after SBF. The total work increases 52%.

Conclusion
This optimal is between 5wt%TiO 2 and 7wt%TiO 2 . The process favors the formation of calcium titanate bond. It is important to produce hydroxyapatite without carbonates for titanium take its place Figure 10: HAcc TEM-HR micrograph shows hexagonal nanostructure and particle size ~100nm. Figure 10: HAcc TEM-HR micrograph shows hexagonal nanostructure and particle size ~100nm. a b c d Figure 9: Electron diffraction pattern a) HA95cc TEM micrograph shows nanostructure ~100nm, b) HA90cc TEM micrograph shows particle size ~200nm. Electron diffraction shows nanostructure and lightly textured for, c) HA95cc and d) HA90cc. This changing begins at 5% and finishes at 7%.
alongside calcium. The nanometric size (hydroxyapatite and anatase) and crystal structure (hexagonal and tetragonal, respectively) play a fundamental role in the efficient dissemination of titanium into the network of HA. The nanometer HAcc wins elasticity but loses hardness (86%) compared to micro-HA.