1. 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) 1,2rodica_ion2000@yahoo.co.uk Universitatea Valahia din Targoviste1 ICECHIM, 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(NO 3 ) 2.4H 2 O] and ammonium phospate dibasic [(NH 4 )2HPO 4 ] was dissolved in deionized water separately. The dropwise addition of calcium nitrate [Ca(NO 3 ) 2 ] aqueous solution to vigorously stirred ammonium phospate dibasic [(NH 4 )2HPO 4 ] 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 temperaturesMethodSample Calcination temperature ( O C) Concentratio n (M) Reflux after mixing HA18000.1:0.06 HA210000.1:0.06 HA312000.1:0.06 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, 1000 0 C, and 1200 0 C 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 25-550 0 C, with a speed 20 0 C/min in analuminum crucible, TGA analysis was carried out N 2 atmosphere, the temperature range 25-1200 0 C and at a rate of 20 0 C/min in a crucible of alumina (Al2O3) and analysis TGA in air, the temperature range 25-110 0 C 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 1000 0 C, 2000 X Figure 3: Electron microscopy SEM for Hap powder calcined at 1000 0 C, 1000 X Figure 7. TGA analysis in N2, the 25-1200 C, speed 20C/min, Al 2 O 3 crucible Figure 8. TGA analysis in air, the 25-1100 C, speed 20C/min, Al 2 O 3 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 1000 0 C 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)