Sri Asliza M. A, Zaheruddin K, Shahrizal H

Transcription

1 JOURNAL Of NUCLEAR And Related TECHNOLOGIES, Volume 6, No. 1, Special Edition, STUDY THE PROPERTIES OF DENSE HYDROXYAPATITE- EXTRACT FROM COW BONE Sri Asliza M. A, Zaheruddin K, Shahrizal H School of Materials Engineering, Universiti Malaysia Perlis, UNIMAP s Academics Complex -Jejawi (2), Taman Muhibah, Jejawi 26 Arau, Perlis. sriasliza@unimap.edu.my ABSTRACT In this study, natural Hydroxyapatite (HA) was extracted from clean cow bone by treatment with NaOH and heating at high temperature before ground into fine powder. The HA powder were than mixed together with binder for several hours. Dense HA were formed in die steel mould by using uniaxially pressing method. Sample was sintered at different temperature 115, 12, 125 and 13 o C for several hours. The phases of specimen were identified using X-ray diffraction (XRD). The mechanical properties were analyzed using three-point bending testing and the microstructure was observed by scanning electron microscopy. From XRD results, natural HA shows phase of pure HA up to 125 o C and fracture strength results indicated that the mechanical properties of specimen increase as temperature increase. From microstructure observation using SEM, HA specimen shows initial stages of sintering process at temperature 115 o C and show changes in microstructure evolution as temperature increase up to 13 o C. ABSTRAK Dalam kajian ini, Hydroxyapatite semula jadi (HA) telah dikeluarkan daripada tulang lembu bersih oleh rawatan dengan NaOH dan pemanasan pada suhu tinggi sebelum tanah kepada serbuk halus. Serbuk HA adalah daripada dicampur sekali dengan pengikat untuk beberapa jam. HA tebal dibentuk dalam acuan logam acuan dengan menggunakan uniaxially kaedah serangan. Sampel adalah tersinter pada suhu yang berbeza 115, 12, 125 dan 13 o C untuk beberapa jam. Fasa-fasa spesimen dikenal pasti menggunakan belauan sinar-x (XRD). Sifatsifat mekanikal dianalisis menggunakan ujian pembengkokan tiga mata dan mikrostruktur itu telah diperhatikan oleh kemikroskopan elektron imbasan. Daripada keputusan-keputusan XRD, persembahan HA semula jadi fasa HA tulen sehingga 125 o C dan keputusan-keputusan kekuatan patah menunjukkan yang sifat-sifat mekanikal spesimen itu meningkatkan sebagai peningkatan suhu. Daripada pemerhatian mikrostruktur menggunakan SEM, spesimen HA menunjukkan peringkat-peringkat awal pensinteran proses pada suhu 115 o C dan menunjukkan perubahan dalam evolusi mikrostruktur sebagai peningkatan suhu sehingga 13 o C. Keywords: dense, hydroxyapatite, natural, properties, sintering. INTRODUCTION Hydroxyapatite (HA) is widely used in medical fields especially as a bone substitute, due to its good biocompatibility, bioactivity, high osteoconductive and nontoxic properties (Javidi et al., 28). The production of synthetic HA needs very complicated and sophisticated technique during synthesizing process. Whereas extraction of HA from the natural bone is biologically safe and economic since bovine bone is easy to obtained. HA produced from natural bone 175

2 JOURNAL Of NUCLEAR And Related TECHNOLOGIES, Volume 6, No. 1, Special Edition, 29 inherits most properties of the origin bone such as its chemical composition and structures give advantage in surgical applications. Besides, its potential for bone grafting is better than synthetic HA (Hiller et al., 23). The effect of sintering temperature to densification process of compact HA from natural bone was investigated in order to produce dense HA for high load bearing application such as hip bone. In this study the effect of sintering temperature to the physical, phase, microstructure and mechanical properties of sintered dense natural HA were examined. MATERIALS AND METHODS In this study a clean cow bone was cut into small pieces and treated with sodium hydroxide solution in a beaker to remove organics until the colour of bone turn into white. After neutralized with distilled water the bones were dried in oven and heat treated at 8 o C for 3 hours to completely remove organics part. Proteins free HA bone were then ground into fine powder by using planetary ball milling for several hour. The fine cow bone powder was then mixed with polyethylene glycol PEG as binder for 16 hours. The compact bodies of cow bone were prepared by using cold pressed technique under 47MPa load pressure into bar shape form. The sintered bodies were obtained after sintering at different temperatures in the ranges from 115 o C to 13 o C for 3 hours. Phase identification of the raw cow bone and sintered cow bone at different temperatures were determined by X-ray diffraction. The specimen surface microstructure was studied by scanning electron microscope and the density was measured by using Archimedes method. The shrinkage percentage of specimens was determined from the different percentage volume of specimen before and after sintering. The three point bending test was used to measure the fracture strength of sintered specimens. RESULTS AND DISCUSSION Raw materials Figure 1a) presents the XRD analysis for raw cow bone after dried at 15 o C. The result shows a broad peak pattern with poor crystalline intensity of HA phase. From the result, not all the standard peaks of HA form because of organic compounds present which disperses the x-ray radiations. Figure 1b) presents the XRD analysis for raw cow bone after firing at 8 o C. The result shows sharp peaks with high intensity of crystalline pattern after firing. All the XRD peaks match with the standard JCPDS file no of pure HA and no impurity other than HA was detected. This result indicates that all organic substance was completely eliminated. 176

3 JOURNAL Of NUCLEAR And Related TECHNOLOGIES, Volume 6, No. 1, Special Edition, (b) Theta - Scale (a) Hydroxyapatite (JCPDS no 9-432) Figure 1: XRD results for raw cow bone (a) after dried at 15 o C and (b) calcined at 8 o C Shrinkage Figure 2 presents the percentage of shrinkage after sintering process. The shrinkage of 27% at 115 o C was attributed to moisture and organic elimination. At higher temperature, the shrinkage increased to 31% and 46% at 12 o C and 125 o C respectively due to some of particles start coalesced to each other. The maximum shrinkage of 48% was observed at 13 o C related to the pore eliminating and densification. 6 5 Shrinkage (%) Temperature (C) ( o C) Figure 2: Percentage of shrinkage with respect to sintering temperature 177

4 JOURNAL Of NUCLEAR And Related TECHNOLOGIES, Volume 6, No. 1, Special Edition, 29 Density and porosity Figure 3 presents the bulk density and percentage of porosity after sintering at different temperatures. From the graph, as temperature increased the density of specimens increased. Whereas, the porosity percentage decreased as the sintering increased. This reduced porosity led to higher densification. The maximum density of 2.57g/cm 3 achieved for the sample sintered at temperature 13 o C which most of the pores were shrunk. Sintering at lower temperatures caused lower density due to higher pores distribution before all grains completely coalesces to each other. Microstructure From the microstructure observation using SEM, Figure 4 presents micrograph of sintered cow bone at different sintering temperature. The evolution of microstructure can be observed after sintering from temperature 115 o C to 13 o C as shown in Figure 4. Specimen shows early stage of sintering at 115 o C where particles start contact to each other. At 12 o C the sintering was in the end of initial stage where particles had begun to coalesce and contact area between particles increased by neck growth. The second stage of sintering at temperature 12 o to 125 o C corresponds to densification and the removal of most of the specimen porosity. In this stage the development of grains boundaries can clearly observed. Figure 4d) presents very clear grains with mean size of ~3µm and density of 2.57 g/cm 3 shows that the sintering process almost complete and subsequently grain growth occurred at temperature 13 o C. Bulk density (g/cm3) Temperature (C) Figure 3: Bulk density and percentage of porosity with respect to sintering temperature Porosuty (%) 178

5 JOURNAL Of NUCLEAR And Related TECHNOLOGIES, Volume 6, No. 1, Special Edition, 29 a b c d X-ray diffraction results Figure 4: SEM micrographs of dense specimen at different temperatures, a) 115 o C, b) 12 o C, c) 125 o C and d) 13 o C (5k magnification) Figure 5 (a-d) present XRD patterns of specimen sintered at 115 o C, 12 o C, 125 o C and 13 o C. The XRD pattern of sintered cow bone at 115 o C for 3 h shows peaks of pure crystalline HA. When the sintering increased at 12 o C, all the HA peaks were not change up to 125 o C as seen in Figure 5(b-c). However at temperature 13 o C, the HA phase started to decompose to α-tcp at angle 3 o, 31.5 o and 32.8 o (2θ). 179

6 JOURNAL Of NUCLEAR And Related TECHNOLOGIES, Volume 6, No. 1, Special Edition, a) b) c) d) Theta - Scale 4 - File: 4.raw - Type: 2Th/Th locked - Start: 1. - End: Step:.34 - Step time: 71.6 s - Temp.: 25 C (Room) - Time Started: 1 s - 2-Theta: 1. - Theta: 5. - Chi:. - Phi:. - X:. Operations: Strip kalpha2.5 Import Hydroxyapatite α-tcp Figure 5: XRD patterns of specimens at different sintering temperatures a)115 o C, b)12 o C, c)125 o C and d)13 o C. Fracture Strength Figure 6 presents the fracture strength of sintered cow bone at different sintering temperature. It can be observed that with increasing sintering temperature, fracture strength of dense cow bone ceramics significantly increased. From the results, the strength increased from 13MPa to 18.47MPa from temperature 115 o C to 12 o C. At higher temperature the strength increased to 3.4MPa. The maximum strength of 34.5MPa obtained at temperature 13 o C. This was attributed to complete sintering process of specimen with highest density of 2.57 g/cm 3. At lower temperature the higher result of porosity percentage contributed to lower strength of 18

7 JOURNAL Of NUCLEAR And Related TECHNOLOGIES, Volume 6, No. 1, Special Edition, 29 specimens. This result due to incomplete sintering process with high pores distribution on the fracture surface can be observed (Figure 4 (a-c)) Fracture strength (MPa) Temperature (C) ( o C) Figure 6: Fracture strength (MPa) of sintered specimens with respect to sintering temperature CONCLUSIONS Dense compact natural HA was produced via sintering process. The modulus of rapture specimens increased as temperature increased due to decreasing of porosity. The maximum strength of 34.5MPa obtained at temperature 13 o C with mean grain size of 3μm can be clearly observed. There was no HA phase change from 115 o C to 125 o C. However the α-tcp was occurred at temperature 13 o C indicated that HA started to decompose. ACKNOWLEDGEMENT This work was supported by Science fund grant (95-1) from MOSTI. REFERENCES Hiller J. C., Thompson T. J. U., Evison M. P., Chamberlain A. T., Wess T. J. (23) Bone mineral change during experimental heating: an X-Ray scattering investigation. Journal Biomaterials Javidi M., Bahrololoom M. E. and Ma J. (28) Electrophotic deposition of natural hydroxyapatite on medical grade 316L stainless steel. J. Materials Science and Engineering C Nasser Y. Mostafa (27) Characterization, thermal stability and sintering of hydroxyapatite powders prepared by different routes. J. Materials Chemistry and Physics Wei-Jen Shih, Szu-Hao Wang, Wang-Long Li, Min-Hsiung Hon, Moo-Chin Wang (26) The phase transition of calcium phosphate coatings deposited on a Ti 6Al 4V substrate by an electrolytic method. Journal of Alloys and Compounds 181

8 JOURNAL Of NUCLEAR And Related TECHNOLOGIES, Volume 6, No. 1, Special Edition, 29 Jingxian Zhang, Hideaki Tanaka, Feng Ye, Dongliang Jiang, Mikio Iwasa (27) Colloidal processing and sintering of hydroxyapatite. J. Materials Chemistry and Physics Haberko, K., Bucko, M.M., Brzezinska- Miecznik, J., Haberko, M., Mosgava, W., Panz, T., Pyda, A., Jerzyzarebski. (26). Natural Hydroxyapatite - Its behaviour during heat treatment. J. of The European Cer. Soc. [26]