This document summarizes the characterization and corrosion behavior of a Poly(ɛ-caprolactone)/Hydroxyapatite (PCL/HA) composite coating on Ti6Al4V fabricated using a dip-coating technique. The study aims to develop a polymer-ceramic composite coating to improve the adhesion of HA coatings and provide better corrosion protection compared to HA alone. Various concentrations of PCL were tested, and coatings with 30% PCL showed a densely packed structure and the best corrosion resistance based on electrochemical tests. The addition of PCL improved the adhesion of HA and could be a potential coating for biomedical applications.
Similaire à Characterization and Corrosion Behavior of Poly(ɛ-caprolactone)/Hydroxyapatite Composite Coating on Ti6Al4V Fabricated by Dip - Coating Technique
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Characterization and Corrosion Behavior of Poly(ɛ-caprolactone)/Hydroxyapatite Composite Coating on Ti6Al4V Fabricated by Dip - Coating Technique
1. INSPRING CREATIVE AND INNOVATIVE MINDS
::: :I NIN T THHEE N NAAMMEE O OFF A ALLLLAAHH, ,M MOOSSTT G GRRAACCIOIOUUSS, ,M MOOSSTT M MEERRCCIFIFUULL : :::
GARDEN OF KNWOLEGDE AND VIRTUE
Characterization and Corrosion Behavior of
Poly( -caprolactone)/Hydroxyapatite ɛ Composite Coating on
Ti6Al4V Fabricated by Dip - Coating Technique
By :
Mohd Faiz Mohd Yusoff
MW103004
Main-Supervisor :
Prof. Ir. Dr. Mohammed
Rafiq
Co-Supervisor :
Dr. Rafaqat Hussain
2. Presentation Outlines
2
11..00 I INNTTRROODDUUCCTTIIOONN
1.1 Project Background
1.2 Problem Statement
1.3 Objectives
1.4 Scope of Study
1.5 Significance of study
22..00 M MAATTEERRIIAALLSS & & M MEETTHHOODDSS
33..00 R REESSUULLTTSS & & D DIISSCCUUSSSSIIOONNSS
44..00 C COONNCCLLUUSSIIOONNSS
55..00 R REECCOOMMMMEENNDDAATTIIOONN
4. 4
Biomaterial
Natural or synthetic material that aims to replace part of
living tissue or to restore a normal function in biological
environment
Metal Polymer Ceramic Composite
Biocompatibility
The acceptance of the implant material by the
surrounding tissues without producing any undesirable
response from the body and vice versa [1,2]
Bio-inert Bio-degradable
Does not initiate a positive
response when introduced
to the living tissue
Bio-active
Induce positive
interaction with
surrounding tissue
The ability of material to
dissolve in biological
environment and gradually
substituted by new tissue
5. 5
Metals in Biomedical Applications
Metallic biomaterials are most commonly used for load bearing
implant and internal fixation device due to its featured characteristics
such as :
i.Excellent mechanical properties :
High tensile strength
High yield strength
Resistance to cyclic loading (fatigue)
Resistance to time dependent deformation (creep)
i.Biocompatibility (low cyto-toxicity)
ii.High corrosion resistance
The most commonly used metals and alloys for medical devices
application include :
i.Ti and Ti6Al4V
ii.316L Stainless Steels
iii.Co-Cr-based alloys
7. 7
Limitations of Metallic Implants
Bio-inert :
Do not promote the formation of
apatite layer on its surface [3]
Release metallic ions :
May combine with biomolecules and
cause adverse biological reaction [4,5]
Solution
Surface modification:
Coating with bioactive material
• Accelerate bone healing and bonding of the coatings with bone [6,7,8]
• Enhance the corrosion resistance of metallic implant where coating layer
will reduce the release of metallic ions by acting a barrier
• Combine the mechanical benefits of metal alloys with bioactivity of bioactive
materials
Advantages
8. Bioactive ceramic materials
Act as reinforcement in hard tissue and
responsible for the stiffness of bone,
dentine, and enamel.
8
Coating materials
HHyyddrrooxxyyaappaattiittee ( (HHAA))
Chemical Formula : Ca10(PO4)6(OH)2
The most important calcium
phosphate compounds found in
natural hard tissues as mineral phase
Ca/P ratio : 1.67 (similar to the bone)
Osteconductive : Promote
osteointegration & accelerate implant
fixation
9. 9
Deposition Technique
Plasma Spray
What is potential
alternative technique
PLD Sol-Gel
to fabricate HA
coating?
Advantages Disadvantages
PVD EBD
CVD
Dip-Coating
Sputter Coater
Biomimetic
Rapid deposition rate
High processing temperature
induces decomposition of HA[9,10]
Non-uniform coating with
cracks[11]
Good adhesion High cost equipment and demand
elaborate setup
Commercial
Technique
What is potential
alternative technique
to fabricate HA
coating?
10. 10
Deposition Technique
Advantages Disadvantages
Solution: Post heat treatment
Solution: Post heat treatment
(sintering)
(sintering)
i.Improve the coating adhesion
ii.Densify coating layer
iii.Eliminate porosity
i.Improve the coating adhesion
ii.Densify coating layer
iii.Eliminate porosity
Dip-Coating
Inexpensive equipment & simple
setup
Poor adhesion between the
coatings and metallic substrates
Uniformity of deposition [12]
Low processing temperature
Ability to coat complex substrate
[13]
Ability to control coating amount
and thickess
Alternative
Technique
11. Effect of high sintering temperature during heat treatment :
ii. Catalyze the decomposition of HA into
non-crystalline which increased the in-vitro
11
Problem Statement
Sintered in air at 600°C for 1h
Cracks
Sintered in vacuum at 800°C for 1h
i. The formation of cracks on the surface
due to the thermal expansion
coefficient mismatch between the
coatings and substrate during sintering
and cooling [14,15]
Substrate expose to the
high temperature
dissolution rate [16]
iii. Oxidation and impaired mechanical
properties [17]
HOW TO SOLVE ?
Electrochemical study of HA coatings on
stainless steel substrate (Quihua Yuan, 2009)
12. • Poly ( -caprolactone) ɛ [PCL; (C6H10O2)n] is a semi crystalline
aliphatic polyester that can be synthesised by ROP of
monomeric unit "ɛ-caprolactone” with good biocompatibility,
sustained biodegradability, and remarkable mechanical
properties [18,19,20].
• The use of PCL as polymeric binder can help to improve HA
coating and eliminate the need of sintering process to densify
the coating layer.
12
Polymer Binder : Poly (ɛ-caprolactone) (PCL)
13. Objectives
i. To develop a polymer-ceramic composite coating
13
for Ti6Al4V alloy substrate by using dip coating
technique
ii. To study the effect of PCL concentration in HA
coating on deposition technique parameters.
iii. To study the anti-corrosion properties of the
PCL/HA coated Ti6Al4V alloy substrate.
14. 14
Significance of Study
i. An alternative coating technique which is simple,
cost effective yet gives clinically acceptable
results will be developed.
ii. The problem related to the dip coating technique
(poor bonding adhesion) is solved by using
polymeric binder.
15. Scope of Study
Parameter Description
Metallic Substrate Ti6Al4V (Dimension : 10 mm x 10
15
mm x 10 mm)
Deposition Technique Dip Coating ( HTWL-01 Destop Dip
Coater (MTI Cooperation, USA)
HA precursor Ca Precursor : Ca(NO3)2.4H2O
P precursor : (NH4)2HPO4
Polymeric Binder Poly (ɛ-caprolactone) (PCL)
Characterization Analyses XRD, FTIR, SEM
Electrochemical test Potentiodynamic polarization test
and electrochemical impedance
spectroscopy (EIS) test
(VersaSTAT 3, Priceton Applied
Research)
17. 17
Materials
Table 2.1 List of reagent used in the experiment
Name Formula Brand MW (g/mol)
Calcium nitrate tetra hydrate Ca(NO).4HO QRëCTM, AR grade 236.18
322Diammonium hydrogen
(NH)HPOQRëCTM, AR grade 132.06
424 phosphate
Ammonium hydroxide NHOH QRëCTM, AR grade 35.04
4Chloroform CHCl QRëCTM, AR grade 119.38
3Poly (ɛ-caprolactone) pallets [CHO]n Sigma Aldrich, UK -
6102Sodium chloride NaCl Sigma Aldrich, UK 58.44
Sodium bicarbonate NaHCOSigma Aldrich, UK 84.00
3 Calcium chloride CaClSigma Aldrich, UK 110.98
2 Potassium chloride KCl Sigma Aldrich, UK 74.55
Dipotassium phosphate
KHPO.3HO Sigma Aldrich, UK 174.18
242anhydrate
Magnesium chloride
hexahydrate
MgCl2.6H2O Sigma Aldrich, UK 203.30
Sodium sulphate Na2SO4 Sigma Aldrich, UK 142.04
18. Substrate Preparation
12 mm
Cutting
Grinding
4 mm
12 mm
150 - 1000 grit sized silicon
carbide (SiC) paper
Cleaning
Ultrasonically clean in acetone for
15 min
Drying
In oven at 40 °C for 30 min
Storage
Desiccator
19. Synthesis of HA powder : Microwave assisted co-precipitation
method
Ca – Precursor
[Ca] = 1.0 M
P - Precursor
[P] = 0.6 M
Drop wise
Ca - P Mixture
Ca/P : 1.67
Precipitation pH above 10
Refluxing
Microwave oven
30 min ( 20 s ON and 20 s OFF)
Filtration & Washing
Drying 24 h (80°C)
Heat Treatment
Muffle Furnace
900 °C for 3h (heating rate
5°C)
Characterization
XRD & FTIR
20. 1. PCL pallets were dissolved in chloroform at room
temperature for 15 min followed by the addition HA powder
(sieved to 71 μm) as shown in Table 2.2.
20
Preparation of PCL/HA Suspension
Sample
code
HA PCL Solvent Total
volume
(ml)
Weight
(g)
% Weight
(g)
%
i 1.35 90 0.15 10
Chloroform
10
ii 1.20 80 0.30 20
iii 1.05 70 0.45 30
iv 0.90 60 0.60 40
v 0.75 50 0.75 50
2. The ratio of final concentration was 15 % (w/v).
3. Finally, the mixture was stirred at room temperature for 72 h.
21. 21
Dip – coating process
To investigate the effect
of dip coating parameter
on coating efficiency :
i.Withdrawal speed
(mm/min): 40, 80, 120,
160, 200
ii.Number of dips:
(1 -5)
22. 22
Characterization
Viscosity of the suspension :
• Brookfield DV-II Pro Viscometer
Coating thickness :
• Hitachi Tabletop Microscope, TM3000
Phase composition :
• XRD (Bruker D-8 Advance diffractometer)
Functional group :
• FTIR (ALPHA-T, Brucher)
Surface morphology :
• SEM (JOEL JSM-6390 LV)
23. 23
Electrochemical Test
Parameter Description
Equipment Potentiodynamic/galvanostat (VersaSTAT
3, Priceton Applied Research)
Cell electrode Counter : Graphite
Reference : Ag/AgCl
Working : Ti4Al4V
Artificial body fluid Simulated body fluid (SBF)
Exposed surface area of
0.5 cm2
working electrode
Potentiodynamic polarization
test
Scan rate : 1 mV/s
Potential range : -400 mV to +900 mV
Electrochemical Impedance
Spectroscopy (EIS) test
Perturbation amplitude : 10 mV
Frequency range : 105 Hz to 10-3 Hz
27. SEM : Surface Morphology
The surface is not fully covered by HA coating
HHAA 1100 %% PPCCLL//HHAA
3300 %% PPCCLL//HHAA 5500 %% PPCCLL//HHAA
Surface level pores
Free cracks
29. For further
investigation
29
30 % PCL/HA composite coating
SSMM
CCSS
For further
investigation
Surface level pores
Important for promoting
osteointegration &
Important for promoting
osteointegration &
nutrient diffusion
nutrient diffusion
Densely packed
and intact coating
Indicate the bonding
between coating and
Ti6Al4V is enough to
resist the force during
implantation process
Indicate the bonding
between coating and
Ti6Al4V is enough to
resist the force during
implantation process
30. 30
The Effect of Withdrawal Speed and
Number of Dips on Deposition Amount
30 % HA/PCL
31. The coating thickness
increases as the
withdrawal speed increases
31
The Effect of Withdrawal Speed and Number of
Dips on Coating Thickness
30 % HA/PCL
LLaannddaauu--LLeevviisshh eeqquuaattiioonn ::
h : thickness
Ƞ : viscosity
v : withdrawal speed
γ : liquid-vapour surface tension
ρ : density
g : gravitational acceleration
32. 32
XRD
HA
TCP
PCL
30 % HA/PCL
HA
Confirm the
presence of PCL
Scherrer’s Equation
Crystallite size of HA : 18 nm
34. 34
PPT
Sample Ecorr (mVSCE) icorr ( μA/cm2) Rp (MΩcm2)
Ti6Al4V -372.4 2.6827 x 10-7 0.9110
HA -229.1 6.2560 x 10-8 6.9498
30 % PCL/HA -79.24 7.6862 x10-9 15.0987
Noble
direction
4 x
Lower current density
35 x
35. 35
EIS
1.5 orders
Higher Z modulus at lower frequency
displays a better corrosion resistance
on metal substrate
2 orders
37. 37
Conclusion
I. In this study, we have demonstrated that dip coating
technique can be used to obtained homogeneous crack-free
coating of PCL/HA composite coating on Ti6Al4V.
II. Process parameters and polymer concentration were
successfully manipulated to control the deposition
amount and coating thickness.
III. The addition of 30 % PCL to HA considerably improved
the adhesion of HA and resulted in densely packed
coating which provide better corrosion protection when
compared with HA coating making this combination a
potential candidate for biomedical application.
39. 39
RECOMMENDATIONS
In vitro study : cell adhesion, proliferation and
differentiation
40. 40
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Thermal expansion is the tendency of matter to change in volume in response to a change in temperature.
When a substance is heated, its particles begin moving more and thus usually maintain a greater average separation. Materials which contract with increasing temperature are unusual; this effect is limited in size, and only occurs within limited temperature ranges (see examples below). The degree of expansion divided by the change in temperature is called the material's coefficient of thermal expansion and generally varies with temperature.