In this study, for the first time we have developed the composite coatings using sol-gel derived hydroxyapatite [HAP: (Ca)10(PO4)6(OH)2] and magnetite (Fe3O4) on alkali treated Ti-6Al-4V alloy using various concentrations of Fe3O4 nanoparticles such as 1, 3 and 5 wt% respectively. The fabricated composite coatings were characterized by XRD, SEM-EDAX and contact angle measurements. In vitro bioactivity study confirmed that the composite coated Ti-6Al-4V was highly bioactive and induces bone like apatite formation in the presence of Fe3O4 NPs which involves the nucleus formation by developing Fe-OH groups on the surface of coatings. The corrosion resistance study proved that 1 wt% of Fe3O4 with HAP composite coatings exhibit good anticorrosion behaviour than the 3, 5 wt% of composites due to lower Fe-OH groups and uniform with adherent layer which restricts the leaching of ions. Hence, this finding suggested that HAP/Fe3O4 composites coated implants can be used for biomedical applications. © 2016 Elsevier B.V.

Anjaneyulu G-S-G-N

Department of Mathematics

School of Advanced Sciences

Vellore Campus

Vijayalakshmi U

Department of Chemistry

Vellore Institute of Technology (VIT) is a private university located in&nbsp;Tamil Nadu, India. Founded in 1984, as Vellore Engineering College, the institution offers 20 undergraduate, 34 postgraduate, four integrated and four research programs. It has campuses in Vellore, Amravati, Bhopal and Chennai.

VIT is one of the top ranked private universities in India according to NIRF, THE and QS Rankings.&nbsp;Govt. of India has recognized&nbsp;VIT, Vellore as an&nbsp;Institution of Eminence. This has allowed VIT to take independent quality initiatives and move up in world ranking.

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VIT University

Materials Letters

Direct metal laser sintering (DMLS)is an additive manufacturing technique that enables the production of customized and complex shaped stainless steel products. Application of DMLS parts to critical sectors requires enhanced surface properties. Although extensive research has been undertaken by many investigators on γ-alumina coating on conventionally processed SS 316L, there has been no significant exploration of the properties of SS 316 L processed through DMLS process with and without coating. In this study, an attempt has been made to coat γ-alumina ceramics over 316L SS substrate and report its effects. γ-alumina synthesised using sol-gel technique was examined through Fourier-Transform Infrared Spectroscopy and X- Ray Diffractometer. The coating were 28–36.77 μm thick and had amorphous structures. Characterization on coated substrate displayed a 33.87% increases in hardness and 81.91% increase in roughness. The water contact angle of the coated substrate exceeded bare substrate measurements by over 340. I corr value of 0.0967 for coated substrate confirmed the anti-corrosive behaviour, which was found to be very much an essential requirements for this study. Compared with conventional processed SS 316L, the performance of DMLS SS 316L, the performance of DMLS SS 316L bare substrate and coated substrate are mainly governed by properties such as porosity, laser scanning effect, in build residual stress and surface finish. The development of uniform and adherent coating of γ-alumina acts as a mechanical barrier for enhancement of the surface properties which will enlighten the research and applications in the fields of biomedical, aerospace and automobile industries. © 2019 Elsevier Ltd and Techna Group S.r.l.

Ceramics International

Influence of γ-alumina coating on surface properties of direct metal laser sintered 316L stainless steel

Introduction: Achievement of bioactive coatings on metallic implant surface with higher adhesive strength and corrosive resistance was one of the main challenges for the current biomaterial researchers. Hydroxyapatite was one of the promising bioactive ceramic which can be applied as a coating on the metallic substrate due to its similarity with the human bone. Methods: The work describes the in-situ preparation of HAP/f-MWCNTs composite by sol-gel method. MWCNTs were functionalized by acid treatment. HAP composites have been prepared by varying the molar percentage of f-MWCNTs from 1% to 5%. The prepared composites with various concentrations of f-MWCNTs were characterized by FT-IR and XRD for its functional group analysis and phase purity. The morphology of the prepared powder was analyzed using SEM and TEM. In-vitro corrosive behavior on SBF was studied for the coating prepared HAP composite sol on 316L SS. The triple layer composite coating was obtained at the spin speed of 3000 rpm/min and subjected to sintering at 500 °C/2 h. Results: X-ray diffraction results confirmed the formation of pure HAP up to the addition of 3% of f-MWCNTs without any secondary phases. The average crystallite size of the prepared particles was decreased from 40 ± 2.1 to 17 ± 2.5 nm with the addition f-MWCNTs. The morphological studies confirm the incorporation of f-MWCNTs in HAP matrix. The prepared HAP/f-MWCNTs composite efficiently inhibits the growth of the pathogens such as S. Aureus and E.coli. Improved hardness was observed with reinforcement of f-MWCNTs into the hydroxyapatite matrix. Electrochemical studies confirm the HAP/f-MWCNTs composites having increased corrosive resistance properties. The bonding strength of the composite coatings showed improved adhesion to the 316L surface. Conclusion: In this work we have fabricated sol-gel derived anti-microbial composite coating on the 316L substrate by means of spin coating at optimized conditions with higher adhesive strength and improved corrosion resistance. © 2018 Elsevier Ltd and Techna Group S.r.l.

Synthesis and characterization of hydroxyapatite/carboxylic acid functionalized MWCNTS composites and its triple layer coatings for biomedical applications

Coatings using functionalized multi-walled carbon nanotubes (f-MWCNTs)/hydroxyapatite (HAP) on 316 L Stainless Steel by electrodeposition at the parameter of “-1.5 V” for 30 min. with three electrode set-up configuration and optimization of various concentrations of f-MWCNTs from 1 to 5% were done to improve the coating characteristics for future biomedical applications. The obtained coatings were characterized by Fourier Transformed-Infra Red spectroscopy (FT-IR) and X-ray diffractometer (XRD) to reveal the phase formation in the composites. With various additions of f-MWCNTs, the HAP phase was found to be retained. The growth of HAP on f-MWCNTs was analyzed by High-resolution Transmission Electron Microscope (HR-TEM) and the morphology of composite was found to be of the needle and flower-like particles. To understand the corrosion resistance effect of the developed HAP/f-MWCNTs composite in SBF, electrochemical investigations were carried out using Impedance and Tafel polarization analysis. From the results, it was observed that the coatings have enhanced corrosion resistance behavior and bioactivity. In addition, the Vickers Hardness study proved that the prepared HAP/fMWCNTs composite coating was found to have improved hardness value of (Hv) 390.2 ± 8.0. Thus, the electrodeposited composite coating on 316 L SS substrate can be effectively deployed for biomedical applications. © 2018 Elsevier B.V.

Colloids and Surfaces B: Biointerfaces

Electrochemically grown functionalized -Multi-walled carbon nanotubes/hydroxyapatite hybrids on surgical grade 316L SS with enhanced corrosion resistance and bioactivity

Hydroxyapatite (HAP) has tremendous applications in orthopaedics and dentistry fields due to its enhanced biocompatibility and bioactivity. In the present investigation, ethanol-based HAP nanoparticles (NPs) are prepared by sol–gel method using calcium nitrate tetrahydrate and triethyl phosphite, without using any additives or chelating agents. The sol–gel-derived HAP NPs were characterised using FT-IR, XRD, TGA-DTA, SEM-EDAX, ICP-OES and TEM analyses. In vitro cytocompatibility assessment of different concentrations of HAP NPs (200–1000 μg/ml) was performed using cultured NIH-3T3 fibroblast cell for 24–48 h. The results indicated that HAP NPs did not have any cytotoxic effects on NIH-3T3 cells. Further to this study, sol–gel-derived HAP sol was coated as triple layers on the Ti-6Al-4V by spin coating technique and the developed coatings were characterised by SEM-EDAX to determine the surface uniformity, chemical composition and thickness. The surface wettability of the coatings was observed by contact angle measurements. In vitro corrosion test was carried out in SBF solution and confirms that triple layer HAP coatings derived at 3000 RPM and sintered at 500 °C for 2 h exhibit higher corrosion resistance behaviour. This in vitro corrosion study predicts the suitability of the coatings for its long-term applications in medical field. In vitro cytocompatible study proves that HAP coatings on Ti-6Al-4V play a significant role in the enhancement of cell viability with prominent cellular response. © 2017 Informa UK Limited, trading as Taylor &amp; Francis Group.

Materials Technology

Preparation and characterisation of sol–gel-derived hydroxyapatite nanoparticles and its coatings on medical grade Ti-6Al-4V alloy for biomedical applications

Sol-gel derived silica glasses have many promising features, including low-temperature preparation as well as chemical and physical stability. Two silica glasses with Si100 and Si80 composition were prepared to understand the factors contributing to the rate of bioactivity. The effects of pH, solution aging temperature, and molar ratio of H 2O/tetraethyl orthosilicate (TEOS) were studied, and the obtained powder sample was characterized by Fourier transform infrared spectroscopy, X-ray diffraction studies, and scanning electron microscopy. The synthesized silica glasses were deposited on 316L SS by the spin coating method at the optimized speed of 2000 revolutions per minute. The corrosion resistance behavior of the coatings was determined by (1) open-circuit potential vs time of exposure, (2) electrochemical impedance spectroscopy, and (3) cyclic polarization in Ringer's solution. A higher breakdown potential (Eb) and repassivation potential (Ep) value with lower current density was obtained from cyclic polarization. Similar results were observed from impedance analysis with higher charge transfer resistance (Rct) and lower double layer capacitance (Cdl) indicating the corrosion resistance behavior of the coatings compared with the uncoated 316L stainless steel. From the results, it was observed that both Si100 and Si80 glass coatings had a positive effect on the corrosion resistance behavior. An adhesive strength of 46 MPa and 45 MPa was obtained for the Si100 and Si80 coatings, respectively. An accelerated leach out study was carried out by impressing the potential at their breakdown potential to determine the effect of glass coating for long-term contact between the implant and a normal biological medium. © 2012 The Minerals, Metals &amp; Materials Society and ASM International.

Journal	Data powered by TypesetMaterials Letters
Publisher	Data powered by TypesetElsevier BV
ISSN	0167-577X
Open Access	No