surya m.sc thesis

8/6/2019 Surya m.sc Thesis

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CHAPTER -1

INTRODUCTION

1.1. Biomaterials

Biomaterials are materials used for making devices that can interact withbiological systems to coexist for longer service with minimal failure. Biomaterial

is defined as any systemically, pharmacologically inert substance or combination of

substances utilized for implantation within living system to support function of

living tissue [1].

Biomaterials are widely used in repair, replacement or augmentation of

diseased or damaged parts of the musculoskeletal system such as bones, joints and

teeth. The fundamental requirement of a biomaterial is that the material and the

tissue environment of the body should coexist without having any undesirable or

inappropriate effect on each other. Biocompatibility is an essential requirement for

any biomaterial, implies the ability of the material to perform effectively with an

appropriate host response for the desired application. Common medical devices

made of biomaterials include hip replacements, prosthetic heart valves and the less

common neurological prostheses and implanted drug delivery systems.

Biomaterials can be classified into three categories by their macroscopic

surface characteristics or by their chemical stability in the body environment. Theyare bioinert, bioactive and bioresobable.

Bioinert refers to any material that once placed within the human body has

minimal interaction with its surrounding tissue. Examples of bioinert materials are

stainless steel, titanium, alumina, partially stabilized zirconia, and ultra high

molecular weight polyethylene. Generally a fibrous capsule forms around a bioinert

implant.

Bioactive refers to a material, which upon being placed within the human

body interacts with the surrounding bone and in some cases, even with the soft

tissue. An ion exchange reaction between the bioactive implant and surrounding

body fluids results in the formation of a biologically active carbonate apatite layer

on the implant that is chemically and crystallographically equivalent to the mineral

phase of bone. Examples of bioactive materials are hydroxyapatite and bioglass.


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Bioresorbable refers to material that upon placement within the human body

starts to dissolve (resorbed) and is slowly replaced by tissue such as bone.

Examples of bioresorbable materials are synthetic tricalcium phosphate and

polylactic-polyglycolic acid copolymers.

Materials including metals and alloys, polymers, ceramics and composites

with the appropriate physical properties and biocompatibility are chosen for the

fabrication of medical device.

1.1.1 Metals and alloys

Metals and alloys have a wide range of applications including as devices for

fracture fixation, partial and total joint replacement, external splints, braces and

traction apparatus as well as dental amalgams. Although metals exhibit high

strength and toughness, they are susceptible to chemical and electrochemical

degradation. The implant materials may corrode or wear, leading to the generation

of particulate debris, which may in turn aggravate the body environment and elicit

both local and systemic biological responses. Metals and alloys are very important

in implant applications due to its good mechanical properties.

Example: Stainless steel, gold and Ni-Cr alloy [1,2].

1.1.2 Polymers

Polymers are large molecules made up by the repetition of small, simple

chemical units termed as monomers. Polymers are considered for implant

applications in various forms such as fibres, textiles, rods and viscous liquids.

Recently, polymers have been introduced for hip socket replacement in orthopedic

implant applications due to its close resemblance to natural polymeric tissue

components. However, polymers undergo degradation in the body environment due

to biochemical and mechanical factors. This results in ionic attack and formation of

hydroxyl ions and dissolved oxygen, leading to tissue irritation and decrease in

mechanical properties.

Example: Polyethylene, Polyesters and Silicones [2].


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1.1.3 Composite

Composites are mixtures of two or more materials, which in combination,

offer superior properties to the material alone. Composites usually refer to the use

of fibers which are embedded in a plastic. This composites offer high strength with

very little weight [3].

Example: BUS-GMA-quartz/silica filler, PMMA-glass fillers

1.1.4 Ceramics

Ceramics are inorganic compounds between metallic and nonmetallic

elements that can be classified into three categories of biomaterials by their

macroscopic surface characteristics or by their chemical stability in the body

environment. They are nearly inert (carbon, alumina and zirconia), surface reactive

(glass ceramics) and completely resorbable (hydroxyapatite, calcium phosphate).

The limitations of ceramic materials are their low tensile strength and fracture

toughness.

Example: HA, TCP, and Alumina.

Table 1 gives a list of biomaterials used in body implants with their

properties [1,2,3].

Among which, hydroxyapatite (HA), Ca10

(PO4)6(OH)

2was recognized as

the most suitable biocompatible materials since it resembles the mineral component

of bone and teeth.


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Table.1 List of Biomaterials and Applications

Material Applications

Metals and Alloys:

316L Stainless steel

Co-Cr-Mo, Cr-Ni-Cr-Mo

Gold alloys

Fracture fixation, stents, surgical

instruments

Bone and joint replacement dental

implants, dental restoration, heart valves

Dental restorations

Polymers:

Polyethylene

Polyurethanes

Joint replacement

Blood-contacting devices

Composites:

BUS-GMA-quartz/silica filler

PMMA-glass fillers

Dental restorations

Dental restorations

Ceramics:

Alumina

Zirconia

Calcium phosphates

Bioactive glasses

Carbons

Joint replacement, dental implants

Joint replacement

Bone repair and augmentation, surface

coatings on metals

Bone replacement

Heart valves, precutaneous devices,

dental implants

1.2 Structure of bone and teeth

1.2.1 Bone

Bone is the most typical calcified tissue in mammals. It comes in all sorts of

shapes and sizes in order to achieve the various functions of protection and

mechanical support for the body.


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The major inorganic component of bone mineral is a biological apatite,

which can be defined as a non-stoichiometric, ion-substituted calcium deficient

HA [4]. From the material point of view, bone can be considered as an assembly of

distinct levels of seven hierarchical structural units, from the macro- to the micro-and nanoscales (Fig.1), to meet numerous functions [5]. At the nanostructural level,

tiny plate-like crystals of biological apatite in bone occur within the discrete spaces

within the collagen fibrils and grow with specific crystalline orientation along the c-

axes, which are roughly parallel to the long axes of the collagen fibrils.

The apatite growth is somehow limited by these small intercollagenous

spaces, which are approximately 50 nm in length, 25 nm in width and 23 nm thick.

Type I collagen molecules are self-assembled into fibrils with a periodicity of 67nm and with 40 nm gaps between the ends of their molecules, into which the apatite

crystals are placed. A composite of these two constituents forms mineralized fibrils.

This is why bone is usually termed a fiber-reinforced composite of biological

origin, in which nanometer sized hard inclusions are embedded in a soft protein

matrix. Though the size of biological apatite crystals reported in the literature varies

due to different treatment methods and analysis techniques, it is generally around

the nanometric level, with values in the ranges of 3050 nm (length), 1530 nm

(width) and 210 nm (thickness) [6].


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Fig.1 Microstructure of bone


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1.2.2. Teeth

All teeth consist of two parts, the crown and the root. The root is placed in a

socket called he alvesouls in the maxillary (upper) or mandibular (lower) bones,

being covered by a layer of cementum and attached to the bone by the periodontal

membrane (a layer of fibrous connective tissue). A schematic cross section of a

tooth is showin Fig. 2

Fig.2 Schematic diagram of a teeth

The enamel is the hardest substance in the body and consists of 97 wt % (92

vol.%) of relatively large HA crystals (25 nm thick, 40-120 nm wide, 160-1000 nm

long). The remaining 3 wt% (7 vol.%) consists of organic substance and water [7].

The HA crystals in enamel form well-defined rod or prism-like structures of about 4

m in diameter [8]. Dentine is a mineralized tissue whose distribution of organic

matrix and minerals is similar to that of regular compact done. Dentinal tubules (3-5

m in diameter) radiate from the pulpcavity toward the periphery and penetrate

every part of the dentine [9]. Tubules in the longitudinal direction and the interface

is cemented by a protein-polysaccharide complex substance. Pulp is a soft tissue

containing thin collagenous fibers, nerve cells, blood vessels, etc [10].

The layer of cementum surrounding the root varies from 20-50 m at the

cervix to 150-200 m at the apex. Approximately half of the cementum is inorganic

and half is composed of organic material and water [11]. The periodontal

membrane is made of mostly collagenous fibers and glycoprotins (protein-

polysaccharide complex) [12].


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1.3 Hydroxyapatite

Calcium phosphate ceramics are attractive materials for bone replacement,

dental defect filling, bone tissue engineering and drug delivery applications. Table 2

shows several calcium phosphates arranged according to their Ca/P ratio [13].

Among the several calcium phosphates, Hydroxyapatite (HA) with the chemical

formula Ca10(PO4)6(OH)2 is one of the most important bioceramic material.

Hydroxyapatite, also called hydroxylapatite, is a mineral. It is a naturally occurring

form of calcium apatite with the formula Ca5(PO4)3(OH), but is usually written

Ca10(PO4)6(OH)2 to denote that the crystal unit cell comprises two molecules. Pure

hydroxyapatite powder is white. Naturally occurring apatites can however also have

brown, yellow or green colorations, comparable to the discolorations of dental

fluorosis. The theoretical density of hydroxyapatite is 3.16 gcm-2

. HA has been usedfor various biomedical applications like matrices for controlled drug delivery, bone

cements, tooth paste additive, monolithic implants or coatings on metallic implants,

such as Ti alloys, Co-Cr alloys, stainless steels [14]. But its usage at high load

bearing conditions was restricted because of its brittleness property, poor fatigue

resistance and strength. Hence there is a need for improving the mechanical

properties of these materials suitable for clinical applications. Non-medical

applications of HA include packing media for column chromatography, gas sensors,

catalysis and host materials for lasers [15].

Table 2 Calcium phosphates arranged by Ca: P ratio

Name Abbreviation Formula Ca:P

Tetracalcium phosphate TetCP Ca4O(PO4)2 2.0

Hydroxyapatite HA Ca10(PO4)6(OH)2 1.67

Tricalcium phosphate (, , ) TCP Ca3(PO4)2 1.50

Octacalcium phosphate OCP Ca8H2(PO4)6.5H2O 1.33


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Dicalcium phosphate dihydrate

(brushite)

DCPD CaHPO4.2H2O 1.0

Dicalcium phosphate (monetite) DCP CaHPO4 1.0

Calcium phosphate (, , ) CPP Ca2P2O7 1.0Calcium pyrophosphate dihydrate CPPD Ca2P2O7.2H2O 1.0

Heptacalcium phosphate HCP Ca7(P5O16)2 0.7

Tetracalcium phosphate diacid TDHP Ca4H2P6O20 0.67

Calcium phosphate monohydrate MCPM Ca(H2PO4)2.H2O 0.5

1.3.1. Structure of hydroxyapatite

Of the two known crystal forms of HA-monoclinic, space group P21/b, and

hexagonal, space group P63/m-only the hexagonal phase is of practical importance

because the monoclinic form is destabilized by the presence of even small amounts

of foreign ions [16]. The hexagonal structure contains two different cation sites,

Ca(I) and Ca(II), but only one phosphate environment (Ca(I), Ca(II) are used for

stoichiometric apatite; M(I), M(II) are the general symbols for substituted apatites).

The structure can be roughly described as a phosphate assembly crossed by parallel

channels filled by OH- ions and parallel to the crystallographic c-axis (Fig. 3). Thechannel walls are formed of Ca(II) atoms arranged in staggered triangular arrays.

Ca(I) atoms have a different environment and are positioned in columns parallel to

the OH- channels. A unit cell accommodates a formula unit Ca10(PO4)6(OH)2.

Among the 10 cations, the 4 Ca(I)s are tightly bonded to 6 oxygens and less

strongly to the other 3 oxygens (mean Ca(I)O distance 0.255 nm), whereas the 6

Ca(II) atoms are surrounded by 7 oxygens (mean Ca(II)O distance 0.245 nm).

Ca(I) atoms are strictly aligned in columns and any small change in the metal

oxygen interactions affects the entire lattice [17].


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Fig.3 Structure of HAp

1.3.2. Synthetic Hydroxyapatite

HA is a class of bioceramic material frequently used in bone grafting and in

bone drug delivery. It is one of the most widely used biomaterials for various bone

applications because it possesses most of the qualities required for bone tissue

formation. There are a number of methods for processing HA either from natural

sources or from synthetic sources, but these are studies focused on conventionalmicrophase HA. Recently, nanophase HA has received much attention owing to its

superior surface functional properties over its microphase counterpart, particularly

surface area and surface roughness, which are the most imperative properties

required to promote cell adhesion and cell-matrix interactions immediately after

implantation.

Nanostructured materials are defined as materials containing structure

elements (e.g. cluster, crystallites or molecules) with dimentsions in the range 1-100

nm. It is worth mentioning that the nanophase HA is one of the basic buildingblocks of natural bone that occupies about 60 wt.%. It has also been proved that the

nanophase HA, compared to conventional HA, promotes osteoblast adhesion,

differentiation and proliferation, which leads to enhanced formation of new bone

tissue within a short period. The nanophase HA is therefore perceived to be

beneficial in bone tissue engineering as a new generation scaffolding system. HA at


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nano level would have amazing functional properties due to its grain size, large

surface area to volume ratio and ultrafine structure similar to biological apatite,

which would have a great impact on implant cell interaction in body environment.

There are several methods for the synthesis of nanophase HA, which include

wet chemical method [18], solid state reaction [19], hydrothermal method [20],

micro emulsion method [21], mechanochemical method [22] and sol-gel method

[23]. Among these methods, sol-gel synthesis of HA ceramics has recently attracted

much attention, due to its many advantages, which include high product purity,

homogeneous composition and low synthesis temperature.

1.3.3 Sol-gel method

Solgel is a useful process of self-assembly for the synthesis of

nanoparticles. Colloids are suspensions with molecules of 20100 lm in diameter in

a solvent. The colloid that is suspended in a liquid is the sol, and the suspension

that keeps its shape is the gel. Thus, solgels are suspensions of colloids in

liquids that keep their shape. The solgel process involves the evolution of

networks through the formation of a colloidal suspension and gelation of the sol to

form a network in continuous liquid phase. The precursors for synthesising these

colloids normally consist of ions of a metal, but also

sometimes of other elements surrounded by various reactive species, -i.e., the

ligands.

The solgel formation occurs in four stages: (a) hydrolysis, (b) condensation and

polymerisation of monomers to form particles, (c) growth of the particles, (d)

agglomeration of the particles followed by the formation of networks that extend

throughout the liquid medium resulting in thickening, which forms a gel. Upon

drying, trapped volatiles are driven off and the network shrinks as further

condensation may occur. These processes are basically affected by the initial

reaction conditions. By controlling these factors, it is possible to vary the structureand the properties of the solgel derived inorganic network. For instance, with

hydrolysis under controlled conditions, dispersed spherical nanoparticles can be

synthesized.[23]


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1.3.3.1 Microwave irradiation:

Microwave synthesis of materials offers the advantages of heating

throughout the volume and very efficient transformation energy. Microwave

heating is due to the high penetration depths of microwaves its coupling with lossy

materials results in rapid and uniform heating of the entire bulk of the reacting

substance. This turn, minimizes the thermal gradients reduces the time for particle

diffusion and hence the product can be obtained in relatively short time. Compared

with conventional method, microwave synthesis has the advantages of very short

time, small particle size, narrow particle size distribution, and high purity [24].

Microwave heating is fundamentally different from conventional

heating in that the heat is generate internally within the material heating in that is

the generated internally within the material instead of originating from an external

heating and subsequent radioactive transfer [25].

In chemical point of view microwave heating is of higher spatial

distribution of heat or transfer rate in addition it is a very sensitive function of the

material being processed and depends upon such factors size, geometry, and mass

of the sample

Advantages such as rapid heating rates, reduced processing time,

substantial energy savings, and being environmentally cleaner improve properties,

including fine microstructure of products. Consequently HA should via precipitated

in very small nanosized crystallites [26]

1.4. Scope of the work

The objective of present study is to synthesis HA nanoparticle in the

presence of citric acid via microwave heating and its characterization.


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Chapter -2

Experimental

2.1 Chemicals

The chemicals used were analar grade calcium nitrate tetrahydrate

(Ca(NO3)24H2O, 98%), di-ammonium hydrogen phosphate (NH4)2HPO4, 99%),

citric acid monohydrate (C6H8O7.H2O, 99.5%) and ammonia solution (NH4OH,

25%) obtained from Merck. All reagents were used without further purification.

Deionized water was used as the solvent.

2.2 Synthesis

The nanocrystalline HA was prepared by using sol-gel method via microwave

irradiation.[23-25] Briefly, solutions of 1M Ca(NO3)24H2O (23.615 g of

Ca(NO3)24H2O in 100 ml deionized water), 1M C6H8O7.H2O (21.014 g of

C6H8O7.H2O in 100 ml deionized water) and 0.6M (NH4)2HPO4 (7.923 g of

(NH4)2HPO4 in 100 ml deionized water) were separately brought to pH above 10 by

adding NH4OH solution. The calcium nitrate solution was stirred vigorously atroom temperature and the citric acid solution and di-ammonium hydrogen

phosphate solution was added drop wise into this calcium nitrate solution one by

one. The reaction mixture was put into a household type LG microwave oven of

600W power under air atmosphere for 15 min. The final suspension was allowed to

cool to room temperature and then the precipitate was dried in vacuum oven at 90C

for 48h. Finally, the product was ground into a fine powder using a mortar and

pestle. Flow chart for synthesis of nanocrystalline HA is shown in Fig. 3.


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Fig. 3 Flow chart for synthesis of nanocrystalline HA

2.3 Calcination

1M Ca(NO3)2.4H2OpH > 10

1M citric acidpH > 100.6 M (NH4)2HPO4

pH > 10

Mixing undervigorous stirring

Sol-gel

Microwave heating(600 W, 15 min)

Dried (90C, 48h)

White precipitate

Powder

Crushed


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The as-synthesized sample was annealed at 1100 C for three hours at the

heating rate of 2C/min. After 3 hours the sample was cooled at the rate of 3C/min

until reaching 30C.

2.4 Characterization:

2.4.1 X-ray diffraction:

X-ray diffraction (XRD) is a highly developed and documented technique

that is widely used to identify crystalline materials. It can provide quantitative

information about the chemical composition of a sample, containing different

crystalline phase. The technique involves the generation of X-rays within a sealed

tube that is under vacuum. A current is applied to heat the filament contained within

the tube and the number of electrons emitted corresponds to the strength of the

current. The higher the voltage applied, the greater the number of electrons emitted

from the filament. Typically a voltage of 1560 keV is used to accelerate the

electrons towards a target commonly made of copper and upon impact the

production of X-rays that is of a wavelength characteristic of the target is then

collimated and directed onto a material sample.

The sample can be in finely ground powder form or a smoothly surfaced

processed disc. The X-ray signal is recognized by a detector and processed by a

microprocessor or electronically and converted to a count rate. An X-ray scan of the

sample can be produced by changing the angle between the X-ray source, the

sample and the detector at a controlled rate between preset limits.

The distances between planes of atoms that constitute the sample can be

measured and provide a characteristic set of data corresponding to the chemical

composition of the material. Comparison against standard reference patterns and

measurements allows for identification and analysis of the material. Other

advantageous information such as degree of crystallinity and any deviation from

ideal composition or the presence of impurities can be obtained.[27]XRD pattern of synthesized sample was carried out using a Rigaku D/MAX

ULTIMA diffractometer, with voltage and current setting of 40 kV and 30 mA,

respectively and uses of Cu-K radiation (1.5406 ). Crystallographic

identification of the phases of synthesized sample was accomplished by comparing


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the experimental XRD patterns to standards compiled by the International Center

for Diffraction Data (ICDD).

2.4.2 FT-IR study

IR spectroscopy is an analysis technique that provides information on the

vibrations of atomic and molecular units and is a standard analytical method

employed to reveal information of the specific chemistry and the molecular

structure and orientation of a material specimen.[28] The region of the

electromagnetic spectrum that gives rise to IR radiation promotes transitions in a

molecule between vibrational (from near- and midinfrared radiation) and rotational

(far infrared radiation) energy levels of the lowest electronic energy state. The

molecule can absorb the radiation by increasing its own vibrational energy. IR

spectroscopy relates to the ability of the molecule to absorb radiation energy at

certain specific frequencies which match the natural vibrational frequencies of the

molecule occurring in the IR region of the electromagnetic spectrum, during

irradiation with a whole range of IR frequencies. Therefore, chemical bonds and

groups of bonds within a specimen will vibrate at specific frequencies and upon

exposure to IR rays will only absorb the energy at frequencies characteristic to the

material. The transmittance and reflectance of the IR rays by the sample are

translated into peaks producing a spectral pattern that can be compared and

analysed to identify the material.

The FTIR spectra of as-synthesized samples were recorded on Perkin

Elmer spectrophotometer in the wavenumber range of 4000400 cm1 with 1 cm1

resolution by using KBr pellet technique.

2.4.3 Scanning electron microscopy (SEM)

This widely used and much written about technique functions by focusing

and rastering a relatively high energy electron beam (5100 keV) on a materialsurface. Low energy electrons are emitted from each impact spot of the focused

beam. The intensity of the secondary electron emission is a function of the atomic

composition of the sample and the geometry of the features under observation. The

surfaces are imaged by spatially reconstructing the intensity of the secondary

electron emission on a phosphour screen. Only the secondary electrons generated


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near the surface of the bulk material can detected because the shallow penetration

depth of the low energy secondary electrons produced by the primary electron

beam, leading to surface analysis only. Nonconductive specimens are coated with a

thin electrically grounded layer of metal or sputter coated with gold (Au) to

minimise the accumulation of electric charge by the electron beam. Being that the

metal layer is always 300 A thick, the electrons being emitted from the sample

underneath cannot penetrate and it is the surface coating of the metal that is actually

being monitored. A truly conformal metal coat is therefore required to convey a

good representation of the surface geometry. Low voltage SEM offers a lower

electron accelerating voltage of 1 keV so that charge accumulation is unlikely and

nonconductive specimens do not require coating.[29] The synthesized sample was

coated with a thin layer of Gold (Au) by sputtering and then the microstructure of

the samples was examined using a Hitachi S-3000H scanning electron microscope

(SEM).

Chapter -3

Results and Discussion

3.1 XRD analysis

XRD technique is found to be a powerful tool to determine the phase

composition of materials. The XRD pattern of as-synthesized sample is shown in

the Fig . 4. The obtained data form XRD pattern was compared with JCPDS data


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for calcium phosphates. The observed data did not match with the JCPDS data of

any calcium phosphate phases, which indicate the formation of calcium phosphate

phases was inhibited by addition of citric acid during the synthesis. However, as-

synthesized sample contain calcium carbonate and ammonium nitrate as the

crystalline phase along with amorphous calcium phosphate.

The XRD pattern of 1100C calcined sample is shown in the Fig. 5.

This XRD pattern indicates the sample calcined at 1100C consists of HA, -TCP

and CaO. The composition of the present phase in the sample is given in table 4.


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Fig. 4 The XRD pattern of as-synthesized sample


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Fig. 5 The XRD pattern of the 1100C calcined sample

Table 4 The phase composition of calcined sample

Phase present Composition (%)

HA 78.33


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-TCP 15.43

CaO 6.24

The obtained from XRD results indicate that appropriate calcination

is needed for achieving pure calcium phosphate phase.

3.2 FT-IR analysis

The FT-IR spectrum of as-synthesized sample by microwave irradiation is

shown in the Fig. 6.

The peak at 435 cm-1 is assigned to a triply degenerated bending mode, v2 ,

of the O-P-O.[30)

Bands at 606 cm-1 and 1072 cm-1 are assigned to vibration of phosphate

group, PO42-

.

The peak at 542 cm-1 is assigned to racking vibration of COO-.

The Bond at 668 cm-1 is assigned to O-H..O out of plane vibration.

The peaks at 832 cm-1 and 1382 cm-1 are due to N-O bending vibration

modes of NO3- ions.

The peak at 892 cm-1 is assigned to characteristic bending mode (v6 orv2) of

the CO32-

group.

The peak at 1268 cm-1

is due to OH deformation of vibration of COO-

.

The bond at 1613 cm-1 is assigned to asymmetry CO2- stretching vibration.


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The peaks between 2400 cm-1 to 3926 cm-1 are assigned to stretching mode

(vS), librational mode (vL) and translational mode (vT) of the hydroxyl group,

OH.

Fig. 6 FT-IR spectrum of as-synthesized sample

Table 3 The FT-IR assignment for as-synthesized sample

Wavenumber Assignment

4000 3500 3000 2500 2000 1500 1000 5000

20

40

60

80

100

Transmittance

(%)

Wavenumber (cm-1)

435

542

606

668

738

832

892

10721

174

1268

1382

1553

1613

2400

3035

3158

3926


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(cm-1)

435 O-P-O bending modes (v2) of the PO4 group

542 Racking vibration of COO-

606 The triply degenerated v4 bending vibration PO43- ions

668 O-H.O out of plane vibration738 C-O deformation vibration of COO-

832 N-O bending vibration modes of NO3-

892 Characteristic bending mode (v6 orv2) of the CO32- group

1072 Due to presence of HPO42-

1176 C-O Stretching

1268 O-H deformation vibration of COO-

1382 N-O Stretching vibration of NO3- ions

1613 Asymmetry CO2- Stretching

2400-3926 H2O and OH vibration

3.3 SEM-analysis

The SEM pictures of as-synthesized sample with different

magnification are shown in the Fig. 7 and 8. The SEM image indicates that the as-

synthesised sample consist of micrometric particles with irregular morphology.

The irregular or inhomogeneous morphology of as-synthesised sample

is due to the presence of different calcium/citrate/phosphate species. These results

were support the XRD and FT-IR result of as-synthesised sample.


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Fig. 7 The SEM image of as-synthesized sample


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Fig. 8 The SEM image of as-synthesized sample


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Fig. 9 The SEM image of the 1100C calcined sample

The SEM image of calcined sample at 1100C is shown in Fig. 9. This SEM image

indicates the morphology of 1100C calcined sample. Two different morphology

were observed in SEM image of calcined sample which indicate the presence of HA

and -TCP. This result supports the XRD of calcined sample.


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