Nguyen Thu Phuong

Controlling the electrodeposition, morphology and structure of hydroxyapatite coating on 316L stainless steel.

Hydroxyapatite (HAp) coatings were prepared on 316L stainless steel (316LSS) substrates by electrochemical deposition in the solutions containing Ca(NO3)2·4H2O and NH4H2PO4 at different electrolyte concentrations. Along with the effect of precursor concentration, the influence of temperature and H2O2 content on the morphology, structure and composition of the coating was thoroughly discussed with the help of X-ray diffraction (XRD), Scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectra. The in vitro tests in simulated body fluids (SBF) were carried out and then the morphological and structural changes were estimated by SEM and electrochemical techniques (open circuit potential, polarization curves, Nyquist and Bode spectra measurements). Being simple and cost-effective, this method is advantageous for producing HAp implant materials with good properties/characteristics, aiming towards in vivo biomedical applications.

Fabrication of poly (lactic acid)/hydroxyapatite (PLA/HAp) porous nanocomposite for bone regeneration

In this study, a poly (lactic acid)/hydroxyapatite (PLA/HAp) porous nanocomposite was fabricated by melt mixing method. Polyethylene oxide (PEO) was added into the nanocomposite to improve compatibility of HAp in the PLA matrix. A porous structure of the nanocomposite was created by using a salt (NaCl) which leaches in water. The influence of HAps weight, compatibiliser content of porous agent on morphology and mechanical properties of PLA/HAp nanocomposite was investigated by SEM and tensile testing method. The obtained results indicated that the nanocomposite containing 20 wt% HAp, 5 wt% PEO, and an amount of NaCl in proportion with PLA weight (1 : 1) had good mechanical properties with a promising Youngs modulus close to the one of cancellous bone (530 MPa) as well as a high porosity. The invitro tests of nanocomposite in simulated body fluids (SBF) were carried out and then pH of SBF solution, variation of material mass (Δm), morphology and phase structure of the nanocomposite were also estimated. The results showed that pH decreased, and Δm had positive or negative values depending on composition and surface of material formed by HAp crystals and the hydrolysis of PLA during immersion time.

Synthesis of Silica/Polypyrrole Nanocomposites and Application in Corrosion Protection of Carbon Steel

Silica/polypyrrole nanocomposites without dopant (SiO2/PPy) and with oxalate dopant (SiO2/PPyOx) were synthesized using polymerization of pyrrole in the presence of nano SiO2. Synthesized SiO2/PPy and SiO2/PPyOx were characterized by FTIR, SEM, TEM and EDX and their electrical conductivities were determined by CV method through the two-point-electrode without electrolyte. The corrosion protection performance of polyvinylbutyral (PVB) coatings containing SiO2/PPyOx was evaluated and compared with that of pure PVB coatings and of PVB coatings containing SiO2/PPy by electrochemical impedance spectroscopy and adhesion measurement. The results show that electrical conductivities of SiO2/PPy and SiO2/PPyOx were 0.181 and 0.109 S/cm, respectively. The ratio of PPy on SiO2 in SiO2/PPy and SiO2/PPyOx composites was 0.77/1 and the ratio of oxalate on PPy in SiO2/PPyOx composite was 1.24/1. SiO2/PPy and SiO2/PPyOx improved corrosion resistance and adhesion of PVB coatings. The presence of oxalate in SiO2/PPyOx significantly enhanced the effect of SiO2/PPy on the protection performance of PVB coatings.

Treatment of Cd2+ ions using aluminum doped hydroxyapatite (AlHAp) powder.

Pollution of heavy metals in water is an important problem and is attracting the attention of scientists. It affects the health of humans and destroys the environment, therefore removal of heavy metal ions is necessary. This work is about treatment of Cd 2+ ions in the water using aluminum doped hydroxyapatite (AlHAp) powder. The effect of some factors such as contact time, initial Cd 2+ concentration, pH solution and mass of AlHAp on adsorption capacity and efficiency was investigated. The experimental adsorption data showed that the Cd 2+ removal process follows the pseudo-second-order law. The results about the effect of initial Cd 2+ concentration were evaluated using Langmuir and Freundlich adsorption isotherms. Maximum monolayer adsorption capacity was 103 mg/g. Keywords . Aluminum doped hydroxyapatite (AlHAp), Cd 2+ ions, adsorption, adsorbent.

Synthesis of Cu-BTC, from Cu and benzene-1,3,5-tricarboxylic acid (H3BTC), by a green electrochemical method

Abstract A metal organic framework (MOF) material based on Cu-BTC, which is formed from Cu and benzene-1,3,5-tricarboxylic acid (H3BTC), with 1D and 3D structures was synthesized under potential control. Cu-BTC 3D was electrodeposited at an applied potential of 5 V using tetrabutylammonium tetrafluoroborate (TBATFB) as electrolyte during 10–60 min. Hydration showed that the phase structure of Cu-BTC 3D did not change after a short time of immersing in water and that the specific surface area increased from 48 m2/g to 371 m2/g. In contrast, with a long time of hydration (more than 4 h), Cu-BTC was destroyed and a dehydration process could not recover the Cu-BTC structure.

ELECTRODEPOSITION OF CO-DOPED HYDROXYAPATITE COATING ON 316L STAINLESS STEEL

Hydroxyapatite (HAp) co-doped by magnesium (Mg), st rontium (Sr), sodium (Na) and fluorine (F) was deposited on the 316L stainles s steel (316L SS) substrate by electrodeposition method. The influences of scannin g potential ranges, scanning times, scanning rates to form MgSrFNaHAp coating were investigated. The analytical results of FTIR, SEM, Xray, EDX, thickness and adhension of the obtained coating at scanning potential ranges of 0 ÷ 1.7 V/SCE; scaning times of 5, scanning rate of 5 m V/s showed that MgSrFNaHAp coatings were single phase crystals of HAp, exhibiting rod s hape with the thickness of 8.9 μm and the adhesion strength reaching 8.38 MPa.

Adsorption behavior of Cd2+ ions using hydroxyapatite (HAp) powder

Abstract Pollution of heavy metals in water can affect the health of humans and the environment; therefore, removal of heavy metal ions is getting the attention of scientists. To reduce the negative impact of heavy metals on human health and the environment, Cd2+ ions present in water were treated using hydroxyapatite (HAp) as adsorbent. The effects of contact time, initial Cd2+ concentration, solution pH, and adsorbent mass on the adsorption capacity and efficiency of HAp were investigated. Cd2+ uptake was quantitatively evaluated using Langmuir and Freundlich adsorption isotherms. The maximum monolayer adsorption capacity was 119 mg/g. The experimental adsorption data were analyzed using three kinetic models: Lagergren’s pseudo-first-order law, McKay and Ho’s pseudo-second-order law, and the intra-particle diffusion model. The results showed that the Cd2+ removal process follows the pseudo-second-order law.

Electrodeposition of sustainable fluoridated hydroxyapatite coatings on 316L stainless steel for application in bone implant

Abstract Fluoridated hydroxyapatite (FHAp) coatings were deposited on 316L stainless steel (316LSS) substrate by the electrodeposition method. Different concentrations of F– ion were incorporated into the apatite structure by adding NaF into the electrolyte solution. The coating was uniform and dense, with thickness of 9.6 µm, and F– ions were doped on HAp with mass percentage of 1.7%; F– concentration was 0.002 M. Results of IR, energy-dispersive X-ray (EDX), X-ray and scanning electron microscopy (SEM) analysis showed that the obtained coatings were single phase crystals of HAp, of a cylinder shape with average size of about 100 nm×30 nm, and characterized for the molecular structure FHAp. The in vitro test of 316LSS, HAp/316LSS and FHAp/316LSS materials in simulated body fluid (SBF) solution was realized with different immersion times. After 21 immersion days in SBF solution, the apatite crystals have a cactus-like shape, and they grow to form a thick block on the surface of FHAp/316LSS leading to the decrease of the corrosion current density during the immersion process in the SBF solution.

The Electrochemical Behavior of TiN/316LSS Material in Simulated Body Fluid Solution.

We report on the fabrication and the electrochemical behavior of TiN film on the 316L stainless steel (316LSS) material in simulated body fluid (SBF) solution for implant application. The characterization results indicate that the coated TiN is completely crystalline with (111) crystal orientation. Electrochemical results of 316LSS and TiN/316LSS material after 21 days of immersion in SBF show that the durability of the TiN/316LSS is much higher than that of 316LSS, which registers a very low corrosion current density (about tens of nA cm(-2)). The formation of hydroxyapatite on the surface of the TiN/316LSS is also confirmed by SEM, EDX, X-ray and IR spectroscopy.