A 10-a editie a Seminarului National de nanostiinta si nanotehnologie

18 mai 2011 Biblioteca Academiei Romane

Aurora Anca Poinescu (poinescua@yahoo.com ) 1, Simona Pop (popsimfc@yahoo.com) 2, Rodica Mariana Ion (rodica_ion2000@yahoo.co.uk) 1,2

Universitatea “Valahia” din Targoviste1ICECHIM, Bucuresti2

THERMAL ANALYSIS AND MICROSCOPIC CHARACTERIZATION OF HYDROXYAPATITE POWDER

OBTAINED BY WET PRECIPITATION

Materials and methods

Chemical reagents used in this work: calcium nitrate with four water molecules [Ca(NO3)2.4H2O] and ammonium phospate dibasic [(NH4)2HPO4] was dissolved in deionized water separately. The dropwise addition of calcium nitrate [Ca(NO3)2] aqueous solution to vigorously stirred ammonium phospate dibasic [(NH4)2HPO4] solution at room temperature for about 1h result a milky and somewhat gelatinous precipitate which was then stirred for 1h. The mixture is sintering at 1000C for 24h. It was then washed and filtered in a filter glass [2].

Table 1. Three samples obtained at different calcination temperatures

0.1:0.06 0.1:0.06 1200 1200 HA3HA3Reflux after Reflux after mixingmixing

0.1:0.06 0.1:0.06 1000 1000 HA2HA2Reflux after Reflux after mixingmixing

0.1:0.06 0.1:0.06 800 800 HA1HA1Reflux after Reflux after mixingmixing

ConcentratConcentration (M)ion (M)

Calcination Calcination temperature temperature

((OOC)C)

SampleSampleMethodMethod

After filtration the compact, sticky filter cake was dried at 800C in laboratory oven. Dried powders was crushed by using mortar and pestle and calcined in alumina crucible at different temperatures: 800, 10000C, and 12000C for 1h [3]. In the figure 1 are presented the wet-chemical process to obtain HAp powder. It has been obtained three hydroxyapatite synthetic samples by varying the calcination temperature with the same molar concentration.

Abstract: This paper studies have been conducted thermal microscopic on hydroxyapatite powders obtained by wet precipitation at room temperature DSC analysis was performed a maximum air temperature between 25-5500C, with a speed 200C/min in analuminum crucible, TGA analysis was carried out N2 atmosphere, the temperature range 25-12000C and at a rate of 200C/min in a crucible of alumina (Al2O3) and analysis TGA in air, the temperature range 25-1100C at the same speed.  By scanning electronmicroscopy images showed crystallites with more spherical clusters and few crystals of 0.1mm in size pores.

Results and discussion

Figure 2: Electron microscopy SEM for Hap powder calcined at 10000C, 2000 X

Figure 3: Electron microscopy SEM for Hap powder calcined at 10000C, 1000 X

Figure 7. TGA analysis in N2, the 25-1200 C, speed 20C/min, Al2O3 crucible

Figure 8. TGA analysis in air, the 25-1100 C, speed 20C/min, Al2O3 crucible

VALAHIA UNIVERSITy of TÂRGOVIŞTE FACULTY OF MATERIALS ENGINEERING, MECHATRONICS AND ROBOTICS

All the conditions of the wet synthesis used in the present work make it possible to obtain pure hydroxyapatite, corresponding to a Ca/P=1.67 ratio and a correct stoichiometry.

The chosen methods was the wet precipitation because the wet-chemical precipitation route is the most talented route owing to its ease in experimental operations, low working temperature, high percentages of pure products and inexpensive equipment requirement.

Conclusion

Figure 4: AFM image of the HA powder calcined at 10000C

Figure 5: AFM analysis of hydroxyapatite powder Figure 6: 3-D representation of the HAp crystals obtained by wet precipitation

References:[1] N. A. Zakharov, I. A. Polunina, K. E. Polunin, N. M. Rakitina, E. I. Kochetkova, N. P. Sokolova, and V. T. Kalinnikov,Calcium Hydroxyapatite for Medical Applications, Inorganic Materials, Vol. 40, No. 6, 2004, pp. 641–648.[2]Naruporn MONMATURAPOJ, Nano-size Hydroxyapatite Powders Preparation by Wet-Chemical Precipitation Route, Journal of Metals, Materials and Minerals. Vol.18 No.1 pp.15-20, 2008[3] Sung, Y., Lee, J. and Yang, J.,Crystallization and Sintering Characteristics of Chemically Precipitated Hydroxyapatite Nanopowder. J. Cryst. Growth. 262 : 467-472, 2004.[4]Lazic, S., Zec, S., Miljevic, N., Milonjic, S., 2001 “The Effect of Temperature on the Properties of Hydroxyapatite Precipitated From Calcium Hydroxide and Phosphoric Acid”, Thermochim.Acta, Volume 374, Issue 1, pp. 13-22;[5]Aurora Anca Poinescu, Rodica Mariana Ion, Inna Trandafir, Elena Bacalum, Constantin Radovici, Obtaining and characterization of a calcium hydroxyapatite, The XV-th International Scientific Conference “Tehnomus”, May 8-9, (2009), Suceava Romania;

Figure 9. DSC analysis in air 25-550C, 20C/min rate., Al crucible

Figure 1: Modified chemical precipitation route for HA powder preparation. (Adapted from Sung)