Stability of Suspensions of Bioactive Particles Using Hybrid Organic–Inorganic Solutions as Dispersing Media

Abstract

Abstract.Functional coatings incorporating different types of particles developed by the sol-gel method have been proposed in the last few years for diverse applications. This work focuses on the preparation of homogeneous coatings prepared from stable suspensions with 10 wt% of glass and glass ceramic particles in a hybrid organic-inorganic solution as dispersing media. For this purpose, the pH was shifted up to 6-7 by adding tetrapropylammonium hydroxide (TPAH) which behaves as a cationic surfactant being probably adsorbed on the particles surface, while the sol maintains stable. Rheological measurements were performed to study the stability of the suspensions prepared at different conditions such as the kind and concentration of dispersant and the pH conditions. After sintering at 450• C/30 min, coatings around 2 µm in thickness were obtained.

Improving the osteointegration and bone–implant interface by incorporation of bioactive particles in sol–gel coatings of stainless steel implants

“…The particle suspensions were prepared by adding 10 wt.% of GC particles to the TEOS-MTES-10% SiO 2 sol. The suspensions were stirred by a high shear mixing in a rotor-stator agitator (Silverson L2R, UK) for 6 min and 15 wt.% of solid surfactant was added [28].…”

Bioactive coatings deposited on titanium alloys

“…The particle suspensions were prepared by the addition of 10% in weight of particles with respect to the solution [9]. The suspensions were stirred by a high shear mixing in a rotor-stator agitator (Silverson L2R, UK) during 6 min.…”

“…The glass was colorless and transparent, and the glassceramic white and translucent [7,9]. The hydroxyapatite was white, opaque and presented good crystallinity [8].…”

Bioactive coatings prepared by sol–gel on stainless steel 316L

“…The addition of tetrapropyl ammonium hydroxide (TPAH, Aldrich) in a concentration of 50 wt% with respect to solids, was used for maintaining glass and glass ceramic particles in suspension. TPAH acts as a cationic surfactant being adsorbed on the particles; it also increases the pH to 6-7 moving the solution away from the isoelectric point and favoring electrostatic repulsion among the particles [8]. The suspension with hydroxyapatite particles was obtained by adding a phosphate ester (Emphos PS21, Whitco, Chem, USA) 2 wt% with respect to solids.…”

“…For this reason, it is important in the development of techniques to improve the corrosion resistance and bioactivity of this material. Coating application by sol-gel technique is a promising alternative due to its properties and tailoring possibilities [2][3][4][5][6][7][8][9][10][11].…”