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Improvement of Hydroxyapatite Sol–Gel Coating on Titanium with Ammonium Hydroxide Addition
Author(s) -
Kim HaeWon,
Kim HyounEe,
Knowles Jonathan C.
Publication year - 2005
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2004.00030.x
Subject(s) - ammonium hydroxide , crystallization , sol gel , calcium hydroxide , hydroxide , polymerization , apatite , materials science , coating , titanium , ammonium , viscosity , chemical engineering , nuclear chemistry , chemistry , inorganic chemistry , mineralogy , polymer , organic chemistry , metallurgy , composite material , nanotechnology , engineering
Small amounts (1–5 vol%) of ammonium hydroxide (NH 4 OH) were added to the ethanol–water‐based hydroxyapatite (HA) sol–gel solution. After aging the sol, a Ti substrate was dip‐coated and heat‐treated at 500°C for 1 h in air. The sol properties were monitored in terms of pH, viscosity, and structure changes with aging time; also, the coating phase and structure on Ti were investigated. During aging, the viscosity of the sol increased while the pH decreased, confirming the polymerization and gelation of the sol. The addition of NH 4 OH altered the sol properties significantly. Increase in the NH 4 OH concentration increased the pH and viscosity of the sol considerably, especially at short aging period, followed by a saturation with further aging. The Fourier transformed‐infrared analysis also confirmed a gradual structure change of the sol with NH 4 OH addition. Such changes in pH, viscosity, and structure bands of the sol driven by the NH 4 OH addition were attributed to the improved polymerization and gelation of the sol. The improved gelation shortened the aging time needed for crystallization of the apatite coating, i.e., increase in the NH 4 OH addition improved the crystallization of the coatings. Within 24 h aging time, the coatings on Ti containing over 3.5 vol% NH 4 OH showed characteristic HA phase and structure bands, at which period no apatite peaks were observed on the HA coating obtained without NH 4 OH addition.