In-vitro corrosion studies of plasma sprayed hydroxyapatite coatings fabricated from coprecipitation synthesized powder

Plasma sprayed bioactive hydroxyapatite (HAp) implants on Ti-6Al-4V substrates have been widely used in load-bearing applications because of their biocompatibility and their intimate contact with bone. In the present study, plasma sm. The present paper discusses detailed corrosion behavior of uncoated and hydroxyapatite coated Ti-6Al-4V in simulated body fluid (Hanks` solution) condition. The HAp coated sample exhibited a smoother anodic curve when compared to uncoated substrate suggesting an improved passive nature of the coated surface. The icorr values for the uncoated and HAP coated samples were found to be 20 μA cm-2 and 14 μA cm-2 respectively. Electrochemical impedance spectroscopy studies showed that the HAp coating applied on to the Ti-6Al-4V alloy does not degrade the corrosion protection of the surface but instead offers an improvement to it.m. HAp coating was deposited on Ti-6Al-4V substrate using atmospheric air plasma spraying system. The as synthesized powder exhibited 97% crystallinity, whereas the coating exhibited a crystallinity of 76%. The coating thickness was ~100 µm and it consisted of mostly fully melted regions and unmelted/partially melted regions. The coating exhibited a surface roughness of 5.7 prayable grade hydroxyapatite powder was prepared by co-precipitation technique using mixture of precipitating agents and avoiding agglomeration process like spray drying. The powder possessed good flowability and exhibited an average agglomerated size of 8

RETINAL SCHIFF-BASE CHROMOPHORE IN THE SURFACTANT SOLUBILIZED WATER POOLS IN CCL4

All-trans-N-retinylidene-n-butylamine Schiff base has been incorporated into AOT/CCl4 reverse micelles of various water pool sizes (omega = 0-20). The nature of interaction between retinal Schiff base and its surroundings in the micellar microenvironment has been investigated by NMR (H-1-NMR and T-1 studies). The Schiff base is found to undergo hydrogen bond interactions with bound water molecules. The results are discussed in terms of the implication of hydrogen bond interactions in retinal proteins, particularly, bacteriorhodopsin

FLUORESCENCE STUDIES OF TRYPTOPHAN AND TRYPTOPHAN-RETINAL SCHIFF-BASE IN REVERSE MICELLAR MATRIX

The fluorescence properties of tryptophan and tryptophan-retinal Schiff base are investigated in a reverse micellar matrix of sodium bis(2-ethylhexyl) sulphosuccinate, a membrane mimetic system. The results are discussed in terms of energy transfer interaction between retinal and tryptophan in the native protein and the conformational aspects of tryptophan residues in the protein

Corrosion protection behaviour of silica–titania hybrid coatings embedded with silica nanoparticles

Hybrid sol-gel coatings prepared using organically modified silanes and corrosion inhibitors are used for the surface protection of metals and alloys. This paper focuses on the corrosion behaviour and compatibility of silica nanoparticles as nanocontainers in silica–titania hybrid system. The surface protection of the alloy is improved by using silica nanoparticles as nanocontainers for cerium (III) inhibitor. The hybrid coating system protected AA2024-T3 alloy effectively against corrosion when immersed in NaCl solution for prolonged hours. The barrier property of the sol-gel film was found to be reinforced due to the presence of cerium nitrate inhibitor in the silica nanoparticles

Silica-alumina based sol-gel coating containing cerium oxide nanofibers as a potent alternative to conversion coating for AA2024 alloy

The current work demonstrates a study on the improved corrosion protection efficiency of a defect-free sol-gel hybrid coating consisting of cerium oxide nanofibers vis-à-vis sol-gel coating containing commercial nanosize ceria particles as corrosion inhibitors. The less researched organically modified silica-alumina (Si-Al) hybrid sol-gel coating containing cerium oxide nanofibers and commercial ceria are synthesized from 3-glycidoxypropyltrimethoxysilane and aluminum-tri-sec-butoxide. The sol-gel matrix containing cerium oxide nanofibers exhibiting Ce mainly in +3 oxidation state exhibits improved corrosion resistance as corroborated by electrochemical impedance spectroscopy. The corrosion property of this sol-gel coating commensurates well with the conventional chromate conversion coating (CCC) as evidenced by the neutral salt spray test. The developed coating exhibits good compatibility with the top primer layer and thus ascertains that the developed Si-Al based sol-gel coating containing cerium oxide nanofibers is a potent alternative to conventional CCC

Ceria nanoparticles vis-à-vis cerium nitrate as corrosion inhibitors for silica-alumina hybrid sol-gel coating

The present work provides a comparative study on the corrosion protection efficiency of defect free sol-gel hybrid coating containing ceria nanoparticles and cerium nitrate ions as corrosion inhibitors. Less explored organically modified alumina-silica hybrid sol-gel coatings are synthesized from 3-glycidoxypropyltrimethoxysilane and aluminium-tri-sec-butoxide. The microemulsion derived nanoparticles and the hybrid coatings are characterized and compared with coatings containing cerium nitrate. Corrosion inhibiting capability is assessed using electrochemical impedance spectroscopy. Scanning Kelvin probe measurements are also conducted on the coatings for identifying the apparent corrosion prone regions. Detailed X-ray photoelectron spectroscopy (XPS) analysis is carried out to comprehend the bonding and corrosion protection rendered by the hybrid coatings

Sol-gel based organic-inoganic hybrid coatings for corrosion protection of aerospace aluminium alloy

Aluminum alloy 2024 is the most commonly used aircraft alloy because of its high damage tolerance, relatively high tensile strength and high strength to weight ratio. These properties are achieved by appropriate alloying with copper and magnesium which, in addition to strengthening phases, form copper -and magnesium- containing constituent particles. However, the presence of these alloying elements makes the alloy susceptible to localized corrosion making it impossible to use it without prior application of a corrosion protection system. Historically, the corrosion protection systems are based on Cr(VI) compounds which are now restricted due to their carcinogenic nature. In this direction, extensive research is pursued on organic–inorganic hybrid silane coatings to replace the toxic Cr (VI) component. In the present study, silica alumina hybrid sol -gel coatings are developed and explored for anticorrosion properties using electrochemical techniques and industry - standard tests. Apart from the basic coating, co rrosion inhibitors are explored to impart active protection to the alloy. The ability of silica - alumina coating to act as reservoir for storage of inhibitors is investigated. The results confirm that coatings containing cerium nitrate inhibitor in an optimum concentration offer superior protection to the surface. X-ray photoelectron and Raman spectroscopy studies provide evidence for the migration of cerium ions from the coating. Improved corrosion protection is attributed to the combined effect of the barr ier nature of the coating and the corrosion inhibiting nature of Ce3+ ions. Further, the role of morphology of the inhibitor when used in the form of solid particles instead of salts is studied. The compatibility of the developed sol -gel layer with subsequ ent top layers of the paint system is also evaluated

All-trans-n-retinylidenetryptamine schiff-base in aot reverse micelles - a novel model system to study secondary interactions in rhodopsins

The fluorescence of all-trans-N-retinylidenetryptamine (1) in AOT solubilized water pool in n-heptane is quenched by the retinyhdene unit. The results are discussed in terms of the nature of secondary interactions in rhodopsins

Multifunctional properties of ceria nanocubes synthesized by a hydrothermal method

Nanosized ceria is an extremely versatile and commercially valuable material because of its industrially important applications. The present work describes the synthesis of ceria nanocubes by a simple hydrothermal method. The size of the synthesized ceria nanocubes are 8–20 nm. The formation of ceria phase has been corroborated by X-ray photoelectron spectroscopy and X-ray diffractometry. Selected area electron diffraction patterns obtained for the nanocubes are also precisely indexed to the cubic ceria phase. The synthesized ceria nanocubes exhibit a high surface area of 26 m2 g−1 and also high catalytic activity. The work also investigates the influence of ceria nanocubes on the corrosion resistance of sol–gel hybrid coatings in 3.5% NaCl solution on AA2024 substrates. The corrosion behaviour of the sol–gel coatings revealed that ceria nanocubes reinforce the barrier properties of the sol–gel coatings and confer longer active protection to the metallic substrate