This is certified that the work involved in the project entitled "PROCESSING OF HYDROXYAPATITE BY BIOMIMETIC PROCESS" by Sakshi Jain (Roll 10608010) in partial fulfillment of the requirements for the award of the Bachelor of Technology Degree in Ceramic Engineering at the National Institute of Technology in Rolkela. it is an authentic work done by her under my supervision and guidance. To the best of my knowledge, the issue embodied in the thesis has not been submitted to any other university/institute for the award of any degree or diploma. Bhattacharyya, Department of Ceramic Engineering, N I T Rourkela, for his valuable advice, time and guidance in the completion of this project.
My heartfelt thanks to all the faculty members for their suggestions during this project work. Technical students and the non-teaching staff for the help and cooperation extended to us. The present work deals with a new chemical precipitation technique for synthesizing hydroxyapatite (HAp-Ca10 (PO4)6 (OH) 2) by a biomimetic method using calcium nitrate tetrahydrate Ca(NO3)2·4H2O and diammonium hydrogen phosphate salts (NH4). 2HPO4 as precursors dissolved in synthetic body fluid (SBF) solutions at 37°C and pH of 7.4.
The crystalline phase, chemical composition and crystallite size of the samples obtained, calcined at different temperatures 560°C, 750°C, 850°C, 1000°C, 1100°C and 1200°C for 2 hours, were characterized by X-powder jet diffraction (XRD). TG/DSC of raw powder shows that the prepared powder has a phase change in HAp at 450°C and the total weight loss on heating was 9.45%.
Natural Occurrence
Properties
Crystal Structure
At a pH greater than 9, orthophosphoric acid solution is added sparingly to a dilute calcium hydroxide solution/suspension. Another precipitation method used to produce hydroxyapatite involves calcium nitrate, diammonium hydrogen phosphate, and ammonium hydroxide. This method results in a faster production rate, with ammonium hydroxide being added to maintain a constant pH.
Compared to the previous method, this approach requires washing the precipitate to remove nitrates and ammonium hydroxide. Taking these factors into account, the production rate of these two techniques is comparable. After wet chemistry, hydrothermal techniques are the second most popular synthesis techniques for producing hydroxyapatite powders.
This method involves a reaction between a mixture of calcium carbonate (CaCO3) and diammonium hydrogen phosphate at high temperatures and pressures such as 275°C and 12000 psi.
Biomimetic Process
The biomimetic process can be used to impart bioactive characteristics to otherwise bioinert biocompatible materials through the deposition of a bone-like apatite layer. This means that, when implanted, the human body has a harder time recognizing the implant as a foreign object, thus reducing the chance of rejection. For implants in orthopedics or dental applications, such as femoral and maxillary facial prostheses, which are typically made of titanium or cobalt alloys, the layer of apatite deposited on the surface of the implant will increase the degree to which bone bonds to them. .
CHAPTER 2~ LITERATURE REVIEW
Hench et al [5] provided the basic idea for dense and porous hydroxyapatite and its different processing routes. Various applications of HAp as bioceramics as well as coatings on metal prostheses were also discussed. 3] synthesized nano-HAp using Ca(NO3)2·4H2O and (NH4)3PO4·3H2O as precursors in the presence of polyethylene glycol (PEG).
The study showed that with changing PEG concentrations, the morphology of the powder is affected and the crystallinity is reduced with increasing PEG concentrations. 1] reviewed different forms of calcium phosphates and the tendency to degrade HAp upon heating. It gave the idea of the advantages of using nano HAp and nano β-TCP as bioceramics in the clinical applications.
Out of many possible routes, two most commonly used synthesis routes, namely wet chemical precipitation and hydrothermal reaction, were discussed. He showed that the uniform dispersion of n-HAp in polyamide matrix was possible due to the formation of chemical bond between n-HAp and PA, such as hydrogen bonding. Interfacial bonding and uniform dispersion are important for improving the bioactivity and mechanical properties of the composite material.
15] synthesized hydroxyapatite (HAp) nanoflakes by a biomimetic method using Ca(NO3)2.4H2O and (NH4)3PO4.3H2O as precursors and chondroitin sulfate (ChS) as a matrix. The results showed that the concentration of ChS significantly affects the morphology and growth of HA crystals. Chopped fiber-like HA crystals can be obtained at low ChS concentration, while flake-like HAp crystals can be obtained at high ChS concentration.
The results showed the phase transition from α-tricalcium phosphate (α-TCP) to β-tricalcium phosphate (β-TCP) in tricalcium phosphate/hydroxyapatite (TCP/HAp) composites. It showed that with increasing HA content in the composite, there was an increase in the calcination temperature for the complete phase transition from α-TCP to β-TCP.
CHAPTER 3~ EXPERIMENTAL WORK
Preparation of SBF
Hence, complete precaution to avoid deviation in both preparation steps and the storage temperatures should be maintained. Reagents (Table 1) were added sequentially to 700 mL of H2O, with the restriction that a new precursor (as in Table 1) was added only after the previous addition had completely dissolved. A total of 40 mL of 1M HCl solution was used for pH adjustments during the preparation of 1L SBF solution.
15 ml of this acid solution was added just before the addition of 6. reagent (CaCl2.2H2O) to avoid cloudiness. After addition of the 8th reagent ((CH 2 OH) 3 CNH 2 ), the solution temperature was raised from ambient to 37°C. During the titration process, it was necessary to dilute the solution with successive additions of deionized water to make the final volume 1 L.
The prepared sample of SBF solutions should be able to be stored at 5°C for one month without degradation [17].
Preparation of Ca-Hydroxyapatite powder at 37°C in SBF [17]
Page | 23 Ca(NO3)2·4H2O and (NH4)2HPO4 in SBF solution contained in separate beakers at the start of precipitation experiments. As soon as both reagents were dissolved in SBF, immediate formation of fine precipitates occurred as indicated by the slight turbidity of the solution. Page | 25 Following the steps outlined in the process flow diagram (Fig. 1), a solution was now achieved.
This solution is then filtered with Whatman filter paper(41) with the simultaneous addition of distilled water. After one day, the remaining residue was taken in a petridish and kept in the oven for one day. The next day, the dried substance was ground in an agate mortar until it was ground into fine particles.
Calcination
The powder calcined at 750°C was compressed into pellet which was then sintered in a blast furnace at 1000°C, 1100°C and 1200°C with 2 hours soaking at the sintering temperature.
Characterization .1 DSC/ TG
- X-ray diffraction
Specific Surface Area by BET method
Dilatometer
RESULTS AND DISCUSSIONS
- Thermal behaviour of as-prepared HAp
- Phase Analysis of calcined samples
- XRD plot of raw HAp powder
- XRD plot of HAp powder calcined at temperature 560 o C
- Phase Analysis of Sintered Sample
- XRD plot of HAp powder sintered at temperature 1000 o C
- XRD plot of HAp powder sintered at temperature 1200 o C
- Crystallite Size
- Specific Surface Area by BET method
Page | 30 This chapter describes the thermal and phase analysis of hydroxyapatite particles prepared by a new chemical precipitation technique using Ca (NO3)2 4H2O and (NH4)2HPO4 salts dissolved in synthetic body fluid (SBF) solutions at 37oC and a pH of 7.4. It was observed that the first two endothermic peaks at 100°C and 250°C could explain the evolution of absorbed water. Page | 31 HAp peaks, there is a shift in peak position with temperature and the appearance of new peaks (at the arrow marks)).
The XRD of HAp powders prepared by new chemical precipitation technique prepared at different temperatures 560oC, 750oC, 850oC with soaking period of 2 hours are shown in Fig.4 - 7. This powder also shows HAp peaks as in the case of a prepared HAp sample, it is observed that there is a shift in peak position with temperature as well as the appearance of new peaks. New peaks corresponding to β-TCP are also observed to appear.
The volume fraction of HAp decreases and correspondingly the volume fraction of β-TCP increases with increase in calcination temperature. Although the volume fraction of HAp in this sample is less in value compared to sample sintered at 1000oC. Page | 38 The figure above shows that the volume fraction of HAp decreases with increasing temperature, while the volume fraction of β-TCP increases with increasing temperature.
CHAPTER 5~ CONCLUSION
SCOPE FOR FURTHER WORK
