Electrochemically deposited hydroxy apatite (HA) coatings were produced on Ti-6Al-4V substrates using aqueous electrolytes. Different coatings were produced by varying the time periods and the source of calcium. Commercially available calcium nitrate and calcium nitrate produced from calcined sea shell were used as sources of calcium in the electrolysis. Various phases of the coatings were characterised by XRD, TEM and FT-IR. Corrosion tests were performed on the coatings by exposing them to uniform corrosion in Simulated Body Fluid (SBF) for 1 month as well as by electrochemical polarization and ac impedance techniques. These tests indicate that HA coatings produced from sea shell source are superior having rough surface and long-term stability in SBF. © 2005 Elsevier B.V. All rights reserved.

Suresh Krishnamoorthy Seshadri

Carbonates

Corrosion protection

Electrodeposition

Electrolytes

Fourier transform infrared spectroscopy

Hydroxyapatite

Surface roughness

Titanium alloys

Transmission electron microscopy

X ray diffraction

CATHODIC DEPOSITION

HYDROXY APATITE COATINGS

Simulated body fluid (SBF)

Protective coatings

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Surface and Coatings Technology

In order to decipher the effect of crystallite size and crystallographic texture on the electrochemical properties of strontium doped calcium phosphate (CaP) coatings, electrodeposition was carried out on two different substrates (Ti and NiTi) and at two different current densities (−1.5 and −3.5 mA cm−2). X-ray diffraction (XRD) studies confirmed the presence of brushite and hydroxyapatite (HaP) phases in varying weight fraction as an effect of varying current densities. XRD line profile analyses showed crystallite size of both CaP phases decrease with increase in current density. X-ray pole figures revealed preferential orientation (texture) of HaP crystallites in [0001] direction and it is pronounced at higher current density for both substrates. Surface characterization and phase analysis were carried using scanning electron microscopy and transmission electron microscopy (TEM). TEM results corroborate the local texture of HaP crystallites, where arc diffraction pattern of (0002) facet was observed. Polarization studies revealed that coating synthesized at higher current density on NiTi having high degree of texture showed icorr of 10−8 A cm−2, which is one order less than that of values obtained for other coatings (10−7 A cm−2). Electrochemical impedance spectroscopy studies exhibited two relaxation features, suggesting the formation of inner barrier and outer porous layer. © The Electrochemical Society

Journal of the Electrochemical Society

Role of crystallographic texture and crystallinity on the electrochemical behavior of nanocrystalline Sr doped calcium phosphate coatings

The development of the calcium phosphate ceramics (CPC) using natural materials such as coral, eggshell, bovine bone, fish bone etc., from Indian origin have been reviewed. The CPCs from natural sources has the benefit that they inherit some of the properties of the raw materials such as the macro-and micro-pore structure, optimal composition, similar morphology etc., as well as the advantage of unlimited world wide availability at a very low raw material cost. Hydroxyapatite (HA), carbonated HA and fluorapatite from natural coral genus "Goniopora" has been obtained. Growth factor loaded coralline HA has been found to significantly accelerate earlystage bone formation in in vivo rabbit model studies. Sea shells have been tested as the source of calcium for electrochemical deposition of HA on titanium implants. Deproteinized hydroxyl carbonate apatite phase was formed by heating adult bovine tibia at 500° C. As eggshell could be easily procured, a great deal of effort has been made to utilize this resource as value-Added CPCs including nanocrystalline HA (OHA), calcium deficient HA (CDHA), TCP, tetracalcium phosphate (TTCP) etc., which are the most widely used bone substitutes. Also OHA showed higher antibiotic delivery and more controlled protein release profile compared to the synthetic apatites. Eggshell derived CPCs were also found to have minor amount of Mg, Sr, Si and Na ions inherited from the eggshell. As these ions are crucial for bio-mineralization of eggshell, the influence of multi-ions substituted CPCs as a potential bioceramic for bone regenerative applications has been emphasised. © 2016 Trans Tech Publications, Switzerland.

Key Engineering Materials

Value added bioceramics: A review of the developments and progress in India

TiO2 coating offers excellent corrosion resistance and the bone mineral hydroxyapatite (HA) offers very good biocompatibility. A suitable combination of these coatings is expected to produce good corrosion resistance as well as biocompatibility of an implant. Functionally graded coatings containing TiO2 and HA were produced on Ti-6Al-4V. Three sets of coatings were produced. The bare alloy is heated for 2 h at 800 °C to get TiO2 layer to get the first coating. The next coating consists of two layers, namely, (a) TiO2 produced by heat-treatment and (b) a second layer containing 50% TiO2 and 50% HA. The third sample contains three layers, namely, (a) TiO2 produced by heat-treatment as the first layer, followed by (b) a layer containing 50% TiO2 and 50% HA and (c) third layer of HA electrochemically deposited above the second layer. These three samples were subjected to corrosion tests in Simulated Body Fluid (SBF). It was found that coating 1 containing the oxide alone had the highest corrosion resistance followed by coatings 2 and 3. Coating 2 provides corrosion resistance and will show better implant-bone bonding. © 2007 Elsevier B.V. All rights reserved.

Materials Chemistry and Physics

Synthesis and corrosion of functionally gradient TiO2 and hydroxyapatite coatings on Ti-6Al-4V

Electrochemically deposited nano-grained calcium phosphate coatings were produced on titanium alloy substrates using aqueous electrolyte maintained at acidic pH. Different coatings were produced by using different cathodic current densities and/or ultrasonic agitation of the electrolytic bath. The structure of the coatings was characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Ultrasonated bath produced coatings containing dicalcium phosphate dehydrate and the grain sizes were in the range of 50-100 nm. © 2006 Acta Materialia Inc.

Scripta Materialia

Electrochemical nano-grained calcium phosphate coatings on Ti-6Al-4V for biomaterial applications

Hydroxyapatite [HAP] and tricalcium phosphate [ß-TCP] are a class of calcium phosphate related ceramic materials that are widely used in tissue regeneration and biomedical applications owing to their excellent bioactivity and biocompatibility. In this investigation, nanocrystalline pure HAP was prepared via sol-gel method by incorporating snail shell as calcium precursor with different phosphorus sources such as triethyl phosphate/phosphite (without using any additives like pH maintaining solutions or gelling agents). Nanocrystalline HAP and biphasic calcium phosphate (HAP + ß TCP) were prepared from triethyl phosphate and triethyl phosphite precursors, respectively. The prepared material was further characterized by powder XRD, IR, Raman spectroscopy, and thermo-gravimetrical analysis to confirm the phase purity, functional groups, and thermal stability. SEM coupled with EDAX was also used to examine the size, shape of particles, and elemental composition of Ca to P ratio in the material. Different phosphorus based HAP has shown rod and spherical shaped surface morphology which was further confirmed by TEM analysis. MTT assay was performed using NIH-3T3 fibroblast cell lines which indicated that the viability was not affected in various concentrations of pure nanocrystalline HAP (12.5-100 μg/ml). This study confirms the improved biocompatibility of biowaste converted HAP which would have implications in biomedical applications. Copyright © Taylor & Francis Group, LLC.

Materials and Manufacturing Processes

Snail Shell Derived Natural Hydroxyapatite: Effects on NIH-3T3 Cells for Orthopedic Applications

Intermetallics

Properties of passive film formed on CP titanium, Ti–6Al–4V and Ti–13.4Al–29Nb alloys in simulated human body conditions

Biomaterials

Theoretical analysis of calcium phosphate precipitation in simulated body fluid

Biomimetic apatite coatings on micro-arc oxidized titania

Hydroxyapatite coating on titanium substrate with titania buffer layer processed by sol–gel method

Biomimetic and electrolytic calcium phosphate coatings on titanium alloy: physicochemical characteristics and cell attachment

Hydroxy apatite coatings on Ti-6Al-4V from seashell

Journal	Surface and Coatings Technology
ISSN	02578972
Open Access	No