GRADUATE UNIVERSITY OF SCIENCE AND TECHNOLOGY INSITUTE FOR TROPICAL TECHNOLOGY SUMMARY OF PhD THESIS IN CHEMISTRY ELECTRODEPOSITION OF HYDROXYAPATITE/MODIFY CARBON NAOTUBES ON ALLOYS TO APPLY FOR BONE IMPLANTS Specialization: Theoretical and Physical chemistry Code: 44 01 19 Hanoi 2019 The dissertation completed at: Academic supervisors: Reviewer 1: Reviewer 2: Reviewer 3: INTRODUCTION  Reason to choose the topic Hydroxyapatite (Ca10(PO4)6(OH)2, HAp) is the main inorganic component in human bones and teeth, has high biocompatibility HAp is applied in medicine with different forms: powder, ceramic, composite and coating Synthetic HAp has the same composition in natural bone and has good biocompatibility However, pure HAp coating has a relatively high solubility in physiological environment and poor mechanical properties leading to faster degradation of the material and reducing the fixed ability between the implant material and the host tissue Some reports show that the doping of carbon nanotubes to create HApCNTcomposite significantly improves the mechanical properties of materials such as corrosion resistance and mechanical strength The thesis: "Electrodeposition of hydroxyapatite/modify carbon nanotubes coating on alloys to apply for bone implants" shows investigation to synthesize HAp-CNTsbt coating on 316LSS and Ti6Al4V  Objectives of the thesis: - Selecting of suitable conditions to synthesize HAp-CNTsbt nanocomposite coating on 316LSS and Ti6Al4V - HAp-CNTbt coating has biocompatibility and protection ability for the substrate in comparison with HAp coating • Main content of the thesis: Study on effect of the scanning potential range, scanning rate, number of scans, CNTbt amount, and synthesis temperature on the characteristics of HAp-CNTbt coating Selecting of suitable conditions for synthesie HAp-CNTbt/316LSS and HAp-CNTbt/ Ti6Al4V materials Determination of roughness, elastic modulus and hardness of 316LSS, Ti6Al4V, HAp/316LSS, HAp/Ti6Al4V, HAp-CNTbt/316LSS, and HAp-CNTbt/Ti6Al4V Determination of dissolutione of HAp and HAp-CNTbt coating in 0.9% NaCl solution Research on biocompatibility and electrochemical behavior of 316LSS, Ti6Al4V, HAp/316LSS, HAp/Ti6Al4V, HAp-CNTbt/316LSS, and HAp-CNTbt/ Ti6Al4V in SBF solution CHAPTER 1: OVERVIEW 1.1 Overview for Hydroxyapatite 1.1.1 Properties of Hydroxyapatite 1.1.1.1 Structural properties Hydroxyapatite (HAp) exists in two structural forms: hexagonal (hexagonal) and monoclinic (monoclinic) Hexagonal HAp is usually formed during synthesis at temperatures between 25 and 100 °C The monoclinic form is mainly created by heating the hexagonal HAp at 850 °C in air, then cooling to room temperature 1.1.1.2 Physical properties HAp exists in crystal with some parameters: molar mass of 1004.60 g, density of 3.08 g/cm3, hardness in the Mohs scale by 5, melting temperature of 1760oC, and boiling temperature 2850 oC The dissolution of HAp in the water is 0.7 g/L HAp crystals usually have rodshape, needle-shape, scale-shape, fibrous-shape, spherical-shape, and cylindrical-shape 1.1.1.3 Chemical properties • HAp reacts with acids to form calcium salts and water • HAp is relatively thermally stable, which is decomposed slowly at temperature range of 800C ữ 1200C, to form oxy-hydroxyapatite At bigger temperatures (> 1200°C), HAp is broken down to β - Ca3(PO4)2 (β - TCP) and Ca4P2O9 or CaO 1.1.1.4 Biological properties HAp has a high biological compatibility, non-toxic, non-allergenic to the human body and has high antiseptic properties 1.1.2 Methods of synthesis of hydroxyapatite coating a Physical method The physical method is the method of creating HAp coating from ions or phase transition These methods have the advantage of being able to easily fabricate HAp coating with a thickness of µm Several physical methods are used: plasma, vacuum evaporation and magnetron sputtering [2, 37] b Electrochemical method Electrochemical method has many advantages in making thin coating on metal or alloys for biomedical applications Electrochemical technique is a simple technique that allows the synthesis of HAp coating at low temperatures The obtained HAp coating is of high purity, good adhesion to the substrate and we can control the coating thickness HAp coating with thickness of nm size are synthesized on different substrates by electrochemical method such as: Electrophoresis method, Anode method, Cathode deposition method 1.1.3 Application of HAp 1.1.3.1 Application of HAp powder HAp powder with nano size is mainly used for medicine and calcium supplements In addition, HAp is used as a slow-release nitrogen fertilizer for plants 1.1.3.2 Application of HAp porous ceramic Porous ceramic of HAp is used in making dentures and repairing dental defects, making artificial eyes, making bone graft details and repairing bone defects 1.2.3.3 Application of HAp composite HAp is combined with biodegradable polymers such as polylactic acid, polyacrylic acid, chitosan to create replacement materials for bone 1.2.3.4 Application of HAp coating HAp coating on the suface of biomedical materials is applied in dentistry, orthopedic bone 1.2 Overview of carbon nano tubes materials 1.2.1 Properties 1.2.1.1 Structure of CNT: CNT are graphene sheets which are rolled up to form a hollow cylinder Depending on rolling direction, CNT materials are divided into armchair, zigzag and chiral types 1.2.1.2 Physical properties 1.2.1.2.1 Mechanical properties CNT have a good mechanical property, durable and low density So, they are used as reinforcement for rubber, polymer, and metals to improve durability and abrasion resistance for materials 1.2.1.2.2 Electrical properties The electrical properties of CNT depend strongly on its structure The electrical conductivity of CNTs is corresponding to semiconductor or metal 1.2.1.2.3 Thermal properties CNTs are good thermal conductors, at room temperature the thermal conductivity of CNTs is about 3,103 W / m.K 1.2.1.2.4 Emisivity properties The electronic emissivity ability of CNT is very high 1.2.1.2 Chemical properties About chemical property, CNT are relatively inert To improve the chemical activity of CNT, CNT usually are modified to create surface defects 1.2.2 Application of CNT materials CNT are used in energy storage, electronic, reinforcing materials and medical applications (CNT are used in biosensors, drug delivery, and nanotechnology application for bone implants) 1.2.3 Modification of CNT - CNT is modified by oxidizing agents, a combined reaction, and substitution reaction 1.3 Composite of hydroxyapatite/carbon nano tubes (HAp-CNTbt) HAp-CNTbt composite is synthesized by many different methods The research results show that the presence of CNT improved the mechanical properties for HAp by the increase of elastic modulus and the hardness 1.4 In vitro and In vivo tests The results of biocompatibility of HAp-CNT in Hanks solution or simulated body fluid solution (SBF) show that the material has good biocompatibility with the development of new apatite crystals The results of in vitro test by cells (osteoblast) showed that there is a good growth 1.5 Investigation in Vietnam In Vietnam, there are some reports about HAp powder, coating, ceramic and composite Since 2011, Dinh Thi Mai Thanh et al (Institute of Tropical Technology) investigated on HAp powder, PLA/HAp composite and HAp coating on the surface of 304LSS, 316LSS, TiN/316LSS, Ti6Al4V and CoNiCrMo We realize that, investigation of HAp-CNT coating is quite new in Vietnam This study aims are selection of suitable conditions to synthesize HAp-CNTcoating on the surface of 316LSS, Ti6Al4V substrates by scanning potential method Chapter CONDITION AND EXPERIMENTAL METHOD 2.1 Chemicals and experimental conditions 2.1.1 Chemicals - Ca(NO3)2.4H2O, NH4H 2PO4, NaNO3, NaCl, NaHCO3, KCl, Na2HPO4.2H2O, MgCl2.6H2O, CaCl2, KH2PO4, MgSO4.7H2O, C6H 12O 6, NH4OH, HCl, HNO3 67 % and H2SO4 98 % CNTs: 90 % of pure, d = 20 – 100 nm, L = - 10 µm is produced at Insitute of Material Science - The materials of 316LSS (100×10×2 mm) and Ti6Al4V (12×10×2 mm) were purchased from Gloria Technology Material Company (Taipei, Taiwan) with element components are listed in Table 2.1 and 2.2 Table 2.1 The element component of 316LSS Element Al Mn Si Cr Ni Mo P Fe Component (%) 0.3 0.22 0.56 17.98 9.34 2.15 0.045 69.405 Table 2.2 The element component of Ti6Al4V Element Ti Al V C Fe Component (%) 89,63 6,04 4,11 0,05 0,17 2.1.2 Electrodeposition of HAp-CNTon 316LSS or Ti6Al4V * Preparation of substrate: 316LSS and Ti6Al4V were polished by SiC paper of 600, 800 and 1200 (Japan) After that, they were clearned and dried The working area was limited of cm2 by epoxy * Modification of CNTs: g CNTs were put in a container containing 200 ml of H2SO4 and HNO3 (3:1) acids with h of ultrasonic Then, the mixtre was heated at 110oC for h using a concender CNTs were obtained using centrifuge to neutral pH and dried at 80oC for 48 h Then, 0.05 g CNT or CNTbt was dispersed into two tubes containing 50 mL of Ca(NO3)2 3x10-2 M, NH4H2PO4 1.8x10-2 M, NaNO 0.15 M solution (the solution is used to synthesize HAp coating) with pH o = 4.3 and ultrasound for 20 minutes These two tubes were left on the shelf for days to observe the dispersion of CNT or CNTbt The pH of the two solutions containing CNT and CNTbt were also measured * The different conditions to synthesize HAp and HAp-CNTsbt coating HAp and HAp-CNTsbt coating were synthesized by scanning potential method The electrolyte solution contains 3x10-2 M Ca(NO3)2, 1.8x10-2 M, NH4H 2PO4, and 0.15 M NaNO3 The coatings were synthesized in a cell of three electrodes: the working electrode is 316LSS or Ti6Al4V, The counter electrode of Platinium; and reference electrode of Ag/AgCl (SCE) The factors investigated: Table 2.3 The conditions to synthesize HAp-CNTbt/316LSS and HAp-CNTbt/Ti6Al4V Survey factor Fixed installation factor - Scanning potential: ÷ -1.4 V; Scanning rate of mV/s, scans, 45 oC ÷ -1.5 V; ÷ -1.6 V; ÷ -1.65 V; ÷ - and CNTbt 0.5 g/L 1.7 V; ÷ -1.8 V; ÷ -1.9 V; ÷ -2.0 V and ÷ -2.1 V - Concentration of CNTbt: 0.25; 0.5; 0.75 ÷ -1.65 V (for 316LSS); and g/L ÷ -2.0 V (for Ti6Al4V); mV/s; scans, 45 oC - Synthesis temperature: 30, 45, 60 oC ÷ -1.65 V (for 316LSS); ÷ -2.0 V (for Ti6Al4V); mV/s; scans, CNTbt 0.5 g/L - Scanning rate: 2, 3, 4, 5, and mV/s ÷ -1.65 V (for 316LSS); ÷ -2.0 V (for Ti6Al4V); scans, 45 oC, CNTbt 0.5 g/L - Scanning times: 3, 4, and scans ÷ -1.65 V (for 316LSS); ÷ -2.0 V (for Ti6Al4V); mV/s; 45 oC, CNTbt 0.5 g/L 2.1.3 In vitro test in SBF solution L of SBF solution containing: NaCl (8 g/L); NaHCO3 (0.35 g/L); KCl (0.4 g/L); Na2HPO4.2H2O (0.48 g/L); MgCl2.6H 2O (0.1 g/L); CaCl2 (0.18 g/L); KH 2PO4 (0.06 g/L); MgSO4.7H2O (0.1 g/L) and glucozo (1 g/L) The initial pH is 7.3 Electrochemical behavior of the materials in 50 ml of SBF solution was carried in the cell of three electrodes, at 37 ± o C 2.2 Methods 2.2.1 Electrochemical methods Dynamic scanning method, Method of measuring open-circuit potential and Electrochemical Impedance Spectroscopy 2.2.2 Analysis methods Characteristics of these materials were determined by IR, SEM, EDX, TEM, XRD, AFM, TGA, measuring adhesion, determination of coating mass and thickness, determination of solubility of HAp and HAp-CNTsbt coating, and the methods to measure the mechanical properties of HAp and HAp-CNTsbt materials CHƯƠNG 3: RESULTS AND DISCUSSTION 3.1 Modification of CNTs The IR spectrum of CNTs: C=C at 1630 cm-1, was overlap with the vibracation of –OH group in the water, the vibracation of –OH at 3400 cm-1 The IR spectrum of CNTsbt: the peak of –OH in water at 3400 cm-1 peaks at 1720 cm-1 and 1385 cm-1 characteristic of C=O and C-OH The results confirm that CNTs was modified successfully Figure 3.2 shows that after days soaked in water, CNTs was clumped by Van der Waals forces CNTsbt dispersed well into water due to the presence of –COOH groups on the surface of CNTsbt, which reduces interaction of Van der Waals forces SEM images show that CNTs and CNTsbt have tubular structures §é trun qua(%) CNTsbt 1720 1385 CNTs 4000 1630 3500 3000 2500 2000 1500 1000 500 -1 Sè sãng(cm ) Figure 3.1-3.3 IR spectra, dispersion and SEM images of CNTs and CNTsbt Bảng 3.3 Thành phần nguyên tố CNT CNTbt Nguyên Nguyên tố Nguyên tố tố m% a% m% a% C 85.43 90.84 81.42 85.37 Figure 3.4 EDX spectra of CNTs and CNTsbt O EDX spectrum of CNTs (Figure 3.4) shows Al characteristic peaks of C, O, Fe, Al and Pt Fe (Table 3.1) EDX spectrum of CNTsbt shows Total 9.85 0.89 3.83 100 9.85 0.89 3.83 100 7.86 0.42 0.88 100 7.26 100 characteristic peaks of C and O The modification process of CNTs removed heavy metal catalysis 3.2 Synthesis and characterization of HAp-CNTsbt composite 3.2.1 Effect of snanning potential range Cathode polarization curves of 316LSS and Ti6Al4V (Fig 3.5): ÷ -0,7 V/SCE, i≈ because no reaction occurs -0,7 ÷ -1,2 V/SCE, i increases slightly corresponding to reduction of H+, O2 in water Potential HAp-CNTbt/316LSS> HAp/Ti6Al4V> HAp/316LSS> Ti6Al4V> 316LSS This result confirms the role of HAp and HAp-CNTbt coatings as the germs that promote the development of new apatite crystals 23 NEW CONTRIBUTIONS OF THE THESIS The composite materials of HAp-CNTbt/316LSS and HAp-CNTbt/Ti6Al4V were successfully synthesized by scanning potential method which is the new method with many advantages in manufacturing thin coating on biomedical material Offer suitable conditions for materials synthesis (such as scanning potential range, scanning rate, number of scans, synthesis temperature and CNTbt concentration) The synthesized HAp-CNTbt coating has good biocompatibility in the simulated body fluid solution (SBF) and has good protection ability for the substrate 24 PUBLICATIONS OF THE THESIS Thi Nam Pham, Thi Mai Thanh Dinh, Thi Thom Nguyen, Thu Phuong Nguyen, E Kergourlay, D Grossin, G Bertrand, N Pebere, S J Marcelin, C Charvillat, and C.Drouet, Operating parameters effect on physico-chemical characteristics of nanocrystalline apatite coatings electrodeposited on 316L stainless steel Adv Nat Sci Nanosci Nanotechnol (2017) 035001 (11pp) Thi Mai Thanh Dinh, Thi Thom Nguyen, Thi Nam Pham, Thu Phuong Nguyen, Thi Thu Trang Nguyen, Thai Hoang, David Grossin, Ghislaine Bertrand, and Christophe Drouet, Electrodeposition of HAp coating on Ti6Al4V alloy and its electrochemical behavior in simulated body fluid solution Adv Nat Sci Nanosci Nanotechnol.7 (2016) 025008 (8pp) (ISI) Nguyen Thi Thom, Pham Thi Nam, Nguyen Thu Phuong, Cao Thi Hong, Nguyen Van Trang, Nguyen Thi Xuyen, Dinh Thi Mai Thanh, Electrodeposition of hydroxyapatite/functionalized carbon nanotubes (HAp/fCNTs) coatings on the surface of 316L stainless steel Vietnam Journal of Science and Technology 55(6) (2017) 706-715 Nguyen Thi Thom, Pham Thi Nam, Nguyen Thu Phuong, Dinh Thi Mai Thanh, Investigation of the condition to synthesize HAp-CNTcoatings on 316LSS, Vietnam Journal of Science and Technology 56 (3B) (2018) 50-42 Nguyen Thi Thom, Pham Thi Nam, Nguyen Van Trang, Nguyen Tuan Anh, Pham Tien Dung, Dinh Thi Mai Thanh, Characterization of hydroxyapatite/carbon nanotubes coatings on Ti6Al4V, Vietnam Journal of Chemistry 2018 56(5).602-605 Nguyen Thi Thom, Pham Thi Nam, Nguyen Trung Huy, Cao Thi Hong, Tran Thi Thanh Van, Nguyen Song Hai, Pham Tien Dung, Dinh Thi Mai Thanh, Electrochemical behavior of HAp/CNTs/316LSS coatings into simulated body fluid solution, Vietnam Journal of Chemistry, 2018, 56(4), 452-459 Nguyen Thi Thom, Dinh Thi Mai Thanh, Tran Thi Thanh Van, Pham Thi Nam, Nguyen Thu Phuong, Cao Thi Hong, Vo Thi Kieu Anh, Biomineralization behavior of HAp/CNTs/Ti6Al4V into the simulated body fluid solution, Vietnam Journal of Science and Technology accepted 6/2019 Nguyen Thi Thom, Pham Thi Nam, Nguyen Thu Phuong, Cao Thi Hong, Nguyen Van Trang, Nguyen Thi Xuyen, Camille Pierre, Dinh Thi Mai Thanh, Electrodeposition and characterization of hydroxyapatite/carbon nanotubes (HAp/CNTs) coatings on the surface of 316L stainless steel, Proceeding the 6th Asian symposium on advanced materials: Chemistry, physics and biomedicine of functional and novel materials 9/2017, 479-486 25 ... Thi Thom, Pham Thi Nam, Nguyen Van Trang, Nguyen Tuan Anh, Pham Tien Dung, Dinh Thi Mai Thanh, Characterization of hydroxyapatite /carbon nanotubes coatings on Ti6Al4V, Vietnam Journal of Chemistry... Sci Nanosci Nanotechnol.7 (2016) 025008 (8pp) (ISI) Nguyen Thi Thom, Pham Thi Nam, Nguyen Thu Phuong, Cao Thi Hong, Nguyen Van Trang, Nguyen Thi Xuyen, Dinh Thi Mai Thanh, Electrodeposition of hydroxyapatite/functionalized... physico-chemical characteristics of nanocrystalline apatite coatings electrodeposited on 316L stainless steel Adv Nat Sci Nanosci Nanotechnol (2017) 035001 (11pp) Thi Mai Thanh Dinh, Thi Thom Nguyen,