In-situ HIGH TEMPERATURE XRD ANALYSIS OF SYNTHESIZED CALCIUM PHOSPHATE BIOMATERIAL USING DEHPA AS THE STARTING MATERIAL

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1 JOURNAL Of NUCLEAR And Related ECNOLOGIES, Volume 6, No. 1, Special Edition, In-situ IG EMPERAURE XRD ANALYSIS OF SYNESIZED CALCIUM POSPAE BIOMAERIAL USING DEPA AS E SARING MAERIAL Meor Yusoff Meor Sulaiman and Masliana Muslimin, Materials echnology Group, Industrial echnology Division, Malaysian Nuclear Agency, Kajang, Selangor, Malaysia el: ; meor@nuclearmalaysia.gov.my ABSRAC A process to produce calcium phosphate biomaterial was done using an organic based diethylhexyl phosphoric acid (DEPA) as its starting material. he gel obtained from this reaction was used to study calcium phosphate transformation using in-situ XRD with temperature ranges from room temperature to 1300 o C. he results obtained from this analysis show the following phase transformation sequence gel > β-ca 2 P 2 O 7 > β-cp + A > α-cp + A. β-ca 2 P 2 O 7 was formed at 400 o C and the sample when heated up to 1000 o C, peaks of β- CP and A appeared showing the transformation of the β-ca 2 P 2 O 7 phase. When the sample was heated up further to 1200 o C, β-cp transformed into α-cp. ABSRAK Satu proses bagi menghasilkan bahan bio calcium fosfat menggunakan asid fosforik (DEPA) sebagai bahan permulaan telah dilakukan. Gel yang diperolehi dari tindakbalas ini telah digunakan didalam kajian XRD secara in-situ dengan suhu yang digunakan antara suhu bilik hingga 1300 o C. Keputusan yang di perolehi dari analisis ini menunjukkan turutan transformasi fasa yang berlaku adalah seperti berikut gel > β-ca 2 P 2 O 7 > β-cp + A > α-cp + A. β- Ca 2 P 2 O 7 terbentuk pada suhu 400 o C dan apabila sampel tersebut dipanaskan ke suhu 1000 o C, puncak-puncak dari β-cp and A akan muncul menunjukkan transformasi fasa β-ca 2 P 2 O 7. Apabila sampel tersebut dipanaskan lagi sehingga 1200 o C β-cp ditransformasikan menjadi α-cp. Keywords: in-situ high temperature XRD, β-ca 2 P 2 O 7, β-cp α-cp, A, DEPA INRODUCION Calcium phosphate is one of the most common synthetic biomaterials. ydroxyapatite (A), a calcium phosphate compound with a chemical formula of Ca 10 (PO 4 ) 6 (O) 2, beta tricalcium phosphate (β-cp, Ca 3 (PO 4 ) 2 ) and alpha tricalcium phosphate (α-cp, Ca 3 (PO 4 ) 2 ) are some of the common bioactive calcium phosphate materials (Caroline and Gnanam, 2002, Sinha et al., 51

2 JOURNAL Of NUCLEAR And Related ECNOLOGIES, Volume 6, No. 1, Special Edition, ). Synthesizing of these calcium phosphate compounds can be done by using the direct precipitation, solid state reaction or sol-gel methods. One of the advantages of using the sol-gel method in synthesizing calcium phosphate biomaterial is the uniform distribution of both calcium and phosphate. his can be seen from the homogeneity of the calcium phosphate product that is produced. An example of the sol-gel method is the used of triethyl phosphite with calcium nitrate or calcium ethoxide (Kivrak and Cuneyt, 1998). Biphasic calcium phosphate (BCP), a term referred to the mixture of A and β-cp has of late been widely applied as bioceramics for both bone and dental implant. An advantage of the BCP is its bioresorbability and/or bioactivity, which depends on the solubility of A and β-cp, can be controlled by manipulating the A to β-cp ratio (Caroline and Gnanam, 2002). he transformation of the different calcium phosphate phases is much affected by the sintering temperature. yun-seung Ryu et al (2005) and Kevor et al., 1999 have suggested the following phase transformation for calcium phosphate heated at high temperature: Dried calcium phosphate β-ca(po 3 ) 2 β-cp + A α-cp + A Phase transformation from dried calcium phosphate to β-ca(po 3 ) 2 occurred at 450 o C while when the sample was heated at 700 o C it was further transformed into β-cp and A. Finally the stable α-cp will be formed from the β-cp at 900 o C. In this study, we synthesized calcium phosphate biomaterial from an organic phosphoric acid, diethylhexyl phosphoric acid (DEPA). DEPA is widely used as a solvent extraction agent in the separation and purification of elements. As the formation the commonly used calcium phosphate biomaterials such A, β-cp and α-cp are much depended on the heating temperature, this in-situ XRD analysis study hopes to establish the synthesis temperature for these compounds. EXPERIMENAL Solution of 20% (w/v) calcium hydroxide was prepared by mixing calcium hydroxide salt with distilled water in a glass beaker. A solvent extraction process then proceeded with the used of DEPA and 4MCl as the organic extracting agent and aqueous portion respectively. he organic portion was then retained and mixed with the calcium solution where a brownish gel was formed. he addition of the calcium solution was preceded until the mixture reaching p10, showing the formation of white precipitate. he precipitate was collected through a buchner filter. he solid precipitate was dried overnight in an oven and then calcined at 900 o C in furnace forming a gel (Figure 1). he XRD instrument used for this in-situ study was Panalytical X Pert PRO attached with Anton Parr high temperature attachment. Diffractograms were collected at room temperature, 200, 400, o C. 52

3 JOURNAL Of NUCLEAR And Related ECNOLOGIES, Volume 6, No. 1, Special Edition, 2009 Figure 1: Calcium phosphate gel used in the study RESULS AND DISCUSSION he use of an organic-based phosphoric acid shows a different pathway compared to precipitation or wet method. he hydrocarbon content in DEPA tends to promote the formation of whitish gel during early precipitation stage. his is similar to the sol-gel process where inorganic alkoxide or related hydrocarbon is used. he present of excessive calcium in the gel will eventually make the gel. When this was calcined white powder was formed. Figure 1 shows the XRD diffractogram of an amorphous sample at room temperature. Figure 2: XRD diffractogram of calcium phosphate sample at room temperature 53

4 JOURNAL Of NUCLEAR And Related ECNOLOGIES, Volume 6, No. 1, Special Edition, 2009 = β-ca 2 P 2 O 7 = β-cp Figure 3: In-situ XRD diffractogram for 200, 400 and 700 o C he sample was then heated at 200, 400 and 700 o C and in-situ XRD diffractograms were taken at these temperatures (Figure 3). At these temperatures peaks of β-ca 2 P 2 O 7 are noticeable especially at 700 o C. he presence of this β-ca 2 P 2 O 7 differs from the result obtained by yun- Seung Ryu et al (2005) and Kevor et al., 1999 where they had noted the presence of β- Ca(PO 3 ) 2. his difference may be resulted from the different starting material used in our study. Upon heating the calcium phosphate sample to 800 o C, there seems to be the formation of more peaks. hese peaks may be attributed to the formation of β-cp and A in addition to the earlier β-ca 2 P 2 O 7 phase (Figure 4). Figure 4 also shows that as the heating temperature is increased, more peaks from these three calcium phosphate phases seem to be formed. Another notable pattern that can be seen from Figure 4 is the tendency of β-ca 2 P 2 O 7 peaks to disappear as the temperature increases. = β-cp = A Figure 4: In-situ XRD diffractogram for o C 54

5 JOURNAL Of NUCLEAR And Related ECNOLOGIES, Volume 6, No. 1, Special Edition, 2009 = A = α-cp Figure 5: In-situ XRD diffractogram for o C Figure 5 represents the XRD diffractograms from 1100 o C to 1300 o C. At 1100 o C, all peaks of β- CP disappears and transform to α-cp. his result is also in agreement with the result obtained by yun-seung Ryu et al (2005). From this high temperature in-situ XRD results we can deduce that the transition reaction of calcium phosphate produced from DEPA is in the following sequence and temperatures: GEL Β-CA 2 P 2 O 7 Β-CP + A Α-CP + A 400 o C 1000 o C 1200 o C he use of DEPA as the starting material could produce various precursor compounds based on level of heating temperature. CONCLUSION It is concluded that DEPA can be used as the starting material to produce calcium phosphate biomaterial. he appropriate temperature for the production of a β-cp and A biphasic calcium phosphate is noted from 1000 o C to 1100 o C. At lower temperatures, β-ca 2 P 2 O 7 is found to be co-existed in the BCP while at higher temperatures the β-cp will be transformed to α- CP. ACKNOWLEDGEMEN he authors wish to thank the management of Nuclear Malaysia for their support on this project and also their permission in presenting this paper. We also like to thank Ms Julie Andrianny and Ms Norhaslinda Ee for carrying out the XRD analysis. 55

6 JOURNAL Of NUCLEAR And Related ECNOLOGIES, Volume 6, No. 1, Special Edition, 2009 REFERENCES E. Caroline Victoria and F.D. Gnanam, 2002, Synthesis and charaterisation of biphasic calcium phosphate, rends biomater. Artif. Organs., 16(1), pp A. Sinha et al., 2001, Development of calcium phosphate based bioceramics, Bull. Mater. Sci., 24(6), pp yun-seung Ryu et al., 2005, Variations in structure and composition in magnessium incorporated hydroxyapatite/ β-tricalcium phosphate, J. Mater. Res., 21(2), pp Kevor S. et al., 1999, Phase evolution during the formation of α-tricalcium phosphate, 82(10), pp N. Kivrak and A. Cuneyt as, 1998, Synthesis of calcium hydroxyappatite-tricalcium phosphate (A-CP) composite bioceramicpowders and their sintering behaviours, J. Am. Ceram. Soc., 81(9), X. Yang and Z. Wang, 1998, Synthesis of biphasic ceramics of hydroxyappatite and β- tricalcium phosphate with control phase content and porosity, J. Mater. Chem., 8,