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Thermal sprayed hydroxyapatite splats: nanostructures, pore formation mechanisms and TEM characterization

Paper ID Volume ID Publish Year Pages File Format Full-Text
13024 828 2004 9 PDF Available
Title
Thermal sprayed hydroxyapatite splats: nanostructures, pore formation mechanisms and TEM characterization
Abstract

Microstructure of thermal sprayed hydroxyapatite (HA) splats was characterized using transmission electron microscopy (TEM), and the formation mechanisms of micropores within the splats were investigated with the aid of simulated body fluids (SBF). High-velocity oxy-fuel and direct current (DC) plasma spray techniques were both utilized for the splats’ deposition. The microstructure features of individual HA splats were revealed through TEM observation of as-sprayed, and ion-milled splats. Amorphous calcium phosphate and tricalcium phosphate phases were observed at the splats’ fringes, which indicated that extensive decomposition of HA had occurred at these locations. The fringes of the HA splats are essentially nanostructured (∼20–50 nm grains), while calcium phosphate grains up to 5 μm, depending on flattening state, are present at the center of the splats. Morphological observation classified the pores within the HA splats into three main categories according to distinctive features in their microstructure: open pores, sealed pores and through-thickness pores. It was found that particle velocity with which the particle impinged on the substrate surface, particle melt state, and structure of starting particle (mainly porosity) are the key variables in determining the formation and morphology of the micropores within the flattened splats. Influence of subsequent splats on the pores of prior deposited splat was also studied using an in vitro incubation test in SBF. Obvious pore-sealing action on the open pores was revealed, which was achieved through liquid filling of subsequent droplets. It was postulated that the overall porosity of a bulk coating could be attributed primarily to the sealed pores and flaws among the splats, and, it could be adequately governed through appropriate particle melt state and optimized velocity of the particles during coating formation.

Keywords
Transmission electron microscopy; Microstructure; Micropores; Thermal spray; Splat; Hydroxyapatite; Formation mechanism
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Thermal sprayed hydroxyapatite splats: nanostructures, pore formation mechanisms and TEM characterization
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Publisher
Database: Elsevier - ScienceDirect
Journal: Biomaterials - Volume 25, Issue 17, August 2004, Pages 3463–3471
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us